Strenuous conditions in the Succulent Karoo: honeybees nest in aardvark holes and an alternative pollination system exists for some flowering plants.

By Geoff Tribe & A. David Marais

162 close-up without flies - Version 2

Of the three aardvark burrows found on the farm Zoethoek in the Succulent Karoo north-east of Touwsrivier, two were inhabited by honeybees and the third was still in use by an aardvark. In contrast, none of the 17 aardvark holes inspected recently in mountain fynbos vegetation on Aurora Mountain above the town of the same name (32° 41’ 04’’S 18° 32’ 10’’E) contained honeybee nests. This is because the topography, vegetation and climatic conditions of the two sites differ greatly.

Autumn foraging by the aardvark colony

Fig 1a. Entrance to the aardvark burrow on the plateau at Zoethoek.

Fig 1a. Entrance to the aardvark burrow on the plateau at Zoethoek.

The honeybee nest in the aardvark hole on the plateau was first discovered in May 2013 (Fig. 1a). Exposed combs could easily be seen near the bottom of the burrow (Fig.1b). On a subsequent visit in January 2015, the combs were completely covered with bees and the swarm was actively foraging (Fig.2). The nest was inspected again on the 26th of April 2015. In the interim a propolis wall had been built in front of the combs (Fig. 3). As a result of 20mm of rain having fallen four weeks previously, the bees were actively foraging and white pollen was being brought to the nest – the origin of which was never discovered.

The driest period of the year in the Succulent Karoo is from January through February into March when the number of plants in flower is minimal and accessible water is hard to find. Although Hessea stellaris (Fig. 4), Ornithoglossum undulatum (Fig. 5), and an Oxalis species were in flower, no honeybees were seen to visit them.

Honeybees were soon attracted to water from a tap which was allowed to drip continuously near the shearing shed about a kilometre away (Fig. 6a). Presumably the odours released from the patch of soil dampened by the water indicated its presence to the bees. The fighting amongst the bees indicated that they were from at least two colonies (Fig. 6b); the attacked bees being vastly in the minority.

Carrion flowers and their deceptions

Honeybees however, were not involved in the pollination of five plant species of the carrion flower group which were in flower. Belonging to the Stapelieae, their flowers release foetid odours which mimic their oviposition substrates and thus attract flies for pollination. The most important pollinators of stapeliads belong mainly in the Calliphoridae (blowflies), Sarcophagidae (flesh flies) or Muscidae (houseflies). It is interesting to note that these succulent plants that extend from this semi-arid region into very arid regions, evolved to attract the ubiquitous flies that may be more prevalent than bees in such barren areas. Unlike bees which sense light better in the ultraviolet region, these flowers are a deep red that may be mistaken for meat by flies. The presence of fur-like projections on some flowers such as Stapelia hirsuta (Fig. 7a) may further imitate the appearance of a wounded or dead animal. Some of these flowers may even have yellow or white markings that further improves the resemblance by suggesting fat. In this way, Huernia zebrina (Fig. 7b) attracts blowflies. Flies which breed in dung invariably lay their eggs in clumps in crevices in the dung from which white larvae hatch. Stapelia glanduliflora (Fig. 7c) for instance, has its flowers fringed by vibratile white cilia which move in the slightest breeze and are thought to resemble that of fly maggots. Flies are believed to be attracted to this movement as they are gregarious when depositing eggs. In especially Stapelia species the flies are so deceived that they lay their eggs on the flower, only to have them predated by ants. The flies are attracted by both the appropriate colouration of the plant and the odour which act in concert, the odour profiles being species specific and independent of generic affiliation (Jὔrgens et al. 2006).

S glanduliflora AS098

Fig. 7c. Stapelia glanduliflora has vibratile white cilia which perhaps resemble fly maggots.

Intricate pollination mechanism

All these features may be attractive to flies but the final conviction comes with the odour the plants emit. The chemicals in these odours are not unique to the Stapelieae: they have been identified in some malodorous arums and orchids. Chemical analyses have even shown that there are different blends that conform to odours from cadavers, carnivorous faeces, herbivorous dung and urine. Bees would not be attracted to these flowers but flies are. There may be some selection according to their detection of the chemicals and the structural features of the plant. Only the right size of insect will successfully collect and transfer the pollen because a certain amount of force is needed to remove the pollinarium (Meve & Liede 1994). Probably the results of a low insect count, these plants, in a similar fashion to orchids, place their 200-300 pollen grains in a sac (pollinium). Two such sacs are connected to a central node to form the pollinarium with the two thin rods forming an inverted V-shape. The fly, exploring the flower towards the ‘nectar’ opening, is deployed as the vector for pollination when its proboscis or other part of its anatomy dislodges the sticky pollinarium. The fly may even have been fooled in laying eggs on the flower with the maggots having no hope of maturing. The pollinarium is carried to the next flower where it is detached in specialized grooves as the fly once again probes for liquid at the nectar opening.

Stapeliads in flower on Zoethoek

The five species in flower (i.e. Quaqua acutiloba, Quaqua mammillaris, Huernia barbata, Piaranthus parvulus, and Stapelia surrecta identified by Dr Peter Bruyns) have relatively inconspicuous flowers and only mild odours within this family of large and colourful flowers (Figs 8.a-e).

One species on the farm, but not in flower at the time of this visit, does have a strong carrion odour: Hoodia gordonii (Fig. 9) whose attractant consists of 94 compounds (Jὔrgens et al. 2006) which presumably have the potential of attracting a variety of fly species.

Fig. 9. Hoodia gordonii in flower in the Tanqua Karoo.

Fig. 9. Hoodia gordonii in flower in the Tanqua Karoo.

Though quite spiny, it had been partly consumed by porcupines (Fig.10); presumably because there was little else on which to forage. The Quaqua mammillaris had been partly consumed by baboons which rejected many portions as they too are spiny. Baboons and porcupines appear to have a special liking for the roots of Euphorbia rhombifolia (Fig. 11) which is dug out and consumed over the entire farm.

Fig. 10. Damage caused by a porcupine predating a Hoodia gordonii plant on Zoethoek.

Fig. 10. Damage caused by a porcupine predating a Hoodia gordonii plant on Zoethoek.

Fig. 11. The poisonous Euphorbia rhombifolia in flower, September 2013.

Fig. 11. The poisonous Euphorbia rhombifolia in flower, September 2013.

Ecology of stapeliads

The ecology of the stapeliads is also interesting. After the pollinarium is lodged on the complex central structure of the flower, two seed pods are produced. These eventually dry and split open to reveal small brown to black seeds that are attached to a very fine parachute. The seeds are released and dispersed by wind. The heat generated on the soil surface during the day (where temperatures of 41°C have been recorded) results in strong winds at night. These seeds are blown up against the bases of spiny Ruschia paucifolia bushes together with other debris. Here, in response to rain they germinate within the debris and grow within these spiny bushes which protect them from predators. When conditions, typically in late summer along with some rain, are favourable, these plants flower. Owing to their growth under bushes or in crevices, they need to attract their pollinators. The (mal)odour may not be sensed by flies from afar but the flower may be seen. The Quaqua mammillaris is a larger plant and bears its flowers directly on the fleshy and spiny stems on which the pollinator can see them. The Stapelia surrecta makes its flower visible by placing it on a long pedicle that projects beyond the canopy of the bush.

Migration of animals

Stapeliads are in synchrony with their environment. They respond to sufficient rainfall by flowering from 3 to 4 weeks later. When animals could still migrate in days of old, herds of antelope would follow the rain and the fresh grazing that it produced. No doubt this would support the growth of flies and the mimicry of the smell of dung would be useful for the pollination of the carrion flowers. The phenomenon of a migrating herd was described by George Mossop in 1877 in his book “Running the Gauntlet” on the Transvaal Highveld near the present day town of Davel. One day while out hunting with an elderly Boer by the name of ‘Ghert Visajie’, Mossop saw many thousands of game on the plain. They suddenly began to trot in opposite directions, leaving an open lane of two miles wide as far as the eye could see. He then heard the distant low rumblings of what appeared to be thunder although it was a perfectly clear day. ‘Visajie’ shouted a warning and spurred his horse up the side of a kopje (hillock) where they watched a huge cloud of dust, about two miles wide, rushing towards them. This great cloud of dust came rushing up with the thunder of hoofs making the earth tremble. Then a line of wildebeest came into view, followed by a mass of game of all kinds which took an hour and a half to pass. ‘Visajie’ explained that their grass had been grazed to the ground and now they were moving on to where it had rained in the distance. The game in possession of the grazing made the lane open for them to pass through to new grazing lands further on. This phenomenon would be repeated again and again, with those now in possession of grazing eventually becoming the migrating herd and being let through by the other herd until an annual circle had brought them back again.

Chemicals used in attraction

With such animals are the constant hoards of flies of various species which pester them. The antelope in turn are trailed by predators, especially lions, which follow in their wake. These flies may be biting flies which feed on the blood of their mammalian hosts; feeding on the liquids such as around their host’s eyes or sweat; on the carcasses of the prey brought down by predators; or those flies which breed in the dung of the various mammalian species. The chemical nature of the odours which attract flies consist of oligosulphides (which mimic carrion) and phenol, indole and p-cresol (which mimic faeces). The stapelia attractants can be divided into four groups – those that mimic herbivore faeces (high in p-cresol content but low amounts of polysulphides); carnivore/omnivore faeces or carcass (high polysulphides but low amounts of p-cresol); carnivore/omnivore (high amounts of heptanal + octanal); and urine (hexanoic acid) (Jὔrgens et al. 2006). At this time, several weeks after the rain has fallen, as the animals migrate through the now green region, the stapeliads are in flower and they virtually ‘borrow’ these flies for pollination. Only flies are attracted, for despite the huge diversity and abundance of dung beetle species in southern Africa whose primary attraction is to dung (Tribe and Burger 2011), they are not attracted to stapeliad flowers.

Stapelia leendertziae from the Nelspruit district with accompanying flies.

Stapelia leendertziae from the Nelspruit district with accompanying flies.

Orbea variegata from the south-western Cape with fly pollinator.

Orbea variegata from the south-western Cape with fly pollinator.

Two divergent pollination systems

Within this Succulent Karoo there are thus two entirely divergent systems at play involving specialized pollinators with completely different attractants – that of a scented flower with a reward of sweet nectar and the other of foul smelling carrion. In the former system there appears to be mutualism in that the flowering plants and the pollinator benefit from each other. Honeybees have a well-developed communication system which is able to immediately recruit large numbers of foragers to a transient nectar source unlike that of flies. In the case of the carrion flowers, the flies are exploited – there is no benefit to the flies and their survival clearly depends on other factors but is nevertheless essential for the carrion flowers. Stapeliad flowers are considered as deceptive flowers because they defraud the flies while imitating a substrate for oviposition (Meve & Liede 1994). The ecology of both categories of pollinators is intricately linked to their environment which determines their behaviour in all respects.

The authors:

Dr A David Marais is a Professor in Chemical Pathology at the University of Cape Town Health Science Faculty. Both Dave and Geoff have a mutual interest in the Stapeliads – the carrion flowers which emit a stench and are pollinated by a variety of flies and not by bees!

Dave in action.

Dave in action.

Dr Geoff Tribe is a Specialist Researcher – Entomology, Plant Protection Research Institute (retired), has done research on dung beetles, honeybees, forest entomology, slugs & isopods.

Geoff saving tortoises

Geoff saving tortoises.

References

Bayer, M.B. 1978. Pollination in Asclepiads. Veld & Flora 64(1): 21-23.

Bruyns, P.V. 2005. Stapeliads of Southern Africa and Madagascar Volumes I & II. Umdaus Press, Pretoria, South Africa. 606pp.

Jὔrgens, A., Dὅtterl, S. and Meve, U. 2006. The chemical nature of fetid floral odours in Stapeliads (Apocynaceae-Asclepiadoideae-Ceropegieae). New Phytologist 172: 452-468.

Meve, U. 1994. The genus Piaranthus R.Br. (Asclepiadaceae). Bradleya 12: 57-102.

Meve, U. and Liede, S. 1994. Floral biology and pollination in stapeliads – new results and a literature review. Plant Systematics and Evolution 192: 99-116.

Mossop, G. 1990. Running the Gauntlet. Publisher: Gordon Button. ISBN 0-620-14756-3

Tribe, G.D. and Burger, B.V. 2011. Olfactory ecology. In: Simmons, L.W. and Ridsdill-Smith, T.J. (Eds) Ecology and Evolution of Dung Beetles. Wiley-Blackwell. pp 87-106.

 

The Fates of the Solitary and Sub-Social Bees following a Fire at Cape Point

By Geoff Tribe, Karin Sternberg and Jenny Cullinan

IMG_9793

Solitary and sub-social bees such as the allodapines, anthophorids, xylocopids and megachilids construct their nests in the branches and stems of dead plants. Such nesting sites include the inflorescences of Aloe species and stems of Kniphofia, Watsonia and various Iridaceae species that contain pith which is excavated to form a chamber. In the case of the allodapines, the pith is removed, the entrance is narrowed and the eggs are laid within this chamber so formed. The megachilids have a more elaborate system where pieces of leaves are removed from plants and used to line their cavities. The much larger carpenter bees or xylocopids excavate tunnels in dead branches which are protected from rain, and construct partitions between the individual cells, each of which is provisioned with a lump of a paste consisting of nectar and pollen on which a single egg is laid.

IMG_1763These nesting sites being composed of dead plant material are thus highly flammable in a vegetation type whose existence relies on regular fires at about 15 year intervals to maintain itself. This would indicate that a fire would be highly detrimental to the local existence of these solitary and sub-social bee species. The fates of the solitary bees after the recent fire in Cape Point Nature Reserve following a lightning strike were investigated.

Within the park allodapine bees were found to construct their nests most frequently in the dead branch tips of the pincushion Leucospermum conocarpodendron and the Mimetes fimbriifolius (Fig. 1a+b+c+d) by hollowing out the pith and then artificially constricting the entrance which they defended either with their heads or stings protruding (Fig. 2a+b).

IMG_4924Several such nests could be found on one bush, the number appearing to be determined by the number of tips that had been broken and the pith exposed. The bees were observed collecting nectar and pollen from a wide variety of indigenous plants whose flowers were mostly yellow and the pollen easily obtainable for species which do not possess baskets on their legs to pack the pollen, but instead remove the pollen coating their hairy bodies on their return to their nests (Fig.3a+b). Some of the plant species that they pollinated were very small with tiny flowers and thus play an important, if largely unnoticed, ecological role in the maintenance of the fynbos.

The fire was indeed disastrous for these bees nesting in dead plant material since nearly all the nests were incinerated. Only the distal ends of a few individual nests in thicker tips of the pincushions and Mimetes survived although the entrances had not been reconstructed four weeks later, and the nests were seemingly deserted. Plants which respond to a fire and owe their continued existence to regular fires such as the fire-asparagus Asparagus lignosus, Kniphofia uvaria and Haemanthus sanguineus were in flower within three weeks and were already visited by various solitary bees within this burnt area (Fig. 4 a, b, + c). Had they migrated into this area from the un-burnt fynbos and established new nests? No new nests were observed but singed and still living Leucospermum conocarpodendron and Mimetes fimbriifolius bushes now had dead tips which presumably could provide new nesting sites for immigrant bees.

The ecology of most of these solitary bees is unknown and yet they appear to play an important role within the fynbos. An example of this, not previously recorded is the interaction between the allodapine bees nesting in the tips of L. conocarpodendron and the neddicky (Cistocola fulvicapilla) (Fig.5) bird inhabiting the fynbos. The neddicky feeds on small insects and their larvae (Ginn et al. 1990). IMG_1472In the presence of ants attempting to enter the allodapines’ nests, the allodapines would respond with a high-pitched piping sound and the intruder would invariable leave. This sound was recorded and then replayed in front of individual nests not being harassed by ants. This would result in the resident allodapine appearing at the entrance and similarly piping. Unexpectedly, a neddicky bird was observed moving around these branch tips containing several nests and producing a similar sound to the detriment of the bees which stuck out their heads and were plucked out by the bird and eaten.

Fig. 5. Neddicky, Cistocola fulvicapilla.

Fig. 5. Neddicky, Cistocola fulvicapilla.

The fire occurring at the end of the season when most allodapines of the next generation would have dispersed to construct new nests would result in the local extinction of the bees within the burnt area. Yet the post-fire response of the fynbos plants which came into flower appears to have begun a re-colonization of the area by the solitary bees.

Acknowledgement: We thank SANParks Table Mountain National Park for permission to study these bees within the park.

References

Ginn, P.J., McIlleron, W.G. & Le S. Milstein, P. (Eds) 1990. The Complete Book of Southern African Birds. Struik Winchester, 760pp.

 

Cape Honeybees, Fynbos, and Fires

By Geoff Tribe, Karin Sternberg and Jenny Cullinan

IMG_0007 - Version 2

One of the major influences on the formation and maintenance of the fynbos biome is the periodic occurrence of fires which are regarded as necessary at intervals of every 15 years or so. Fynbos fires can be extremely hot if there is accumulated fuel and a wind driving the fire. Fynbos plants are adapted to fire and respond in various ways including serotiny where fire releases the seeds of various Proteaceae from their fire-resistant seed-capsules after the fire has passed. In response to the smoke these seeds which are stimulated by cooler tempertaures and rain germinate. Other plants may survive as underground bulbs or tubers and take the opportunity of the post-fire period of reduced competition to proliferate, with different species appearing on the surface and flowering in sequential waves.

20150418-031

Figure 1. Aerial view of the swathe of destruction the fire caused in the Cape Point section of Table Mountain National Park in March 2015 (courtesy of Dr Jonathan Ball).

Cape bee nesting sites. The natural distribution of the Cape honeybee (Apis mellifera capensis Escholtz) is extremely limited and closely follows that of the fynbos vegetation of the winter rainfall region (originally covering only 90 000 km²). The Cape honeybee co-evolved with the fynbos and is well adapted to its environment. The wild fire following a lightning strike on 5 March 2015 which cut through a section of Cape Point Nature Reserve before it was extinguished (Fig.1) left a desolation of ash and sand in its wake (Fig. 2).The adaptation of various creatures to fire-prone fynbos gives some insight into the importance in the selection of nesting sites within the fynbos by honeybees. Within this swathe were three natural colonies which had been monitored for nine months prior to the fire. The colonies were between 1 and 2.5kms apart.

Figure 2. The aftermath: ash, sand and blackened skeletons of shrubs.

Figure 2. The aftermath: ash, sand and blackened skeletons of shrubs.

The colonies in the burnt area were visited on 15 May 2015. All three colonies escaped initial destruction by the fire and this was primarily due to where they had established their nests – under boulders at ground level. But none of the colonies escaped totally unscathed and all had declined in vigour and in the number of active foragers. The highest yearly annual wind speed in southern Africa is recorded at Cape Point and, in addition, the now loose sand is being blown into the fully exposed nests which is exacerbating their efforts to survive. The winter rains are delayed and severe downpours could result when they do arrive which could flood the nests with sludge.

The nest of Colony 1 which was constructed deep under a boulder (Fig. 3a) appeared to have escaped relatively unscathed due to the propolis wall which protected the nest but had melted due to the heat from the fire (Fig. 3b). Fourteen combs were visible but the population had dwindled considerably although there was foraging activity with pollen from Serruria sp. growing outside the burnt area being brought back to the nest. Prior to the fire, Colony 1 was fairly protected from the elements by the growth of vegetation around it (Fig. 3c).

Fig. 3a. Colony 1 whose nest under the boulder (the dark area at ground level in the centre) was protected by a propolis wall escaped destruction.

Fig. 3a. Colony 1 whose nest under the boulder (the dark area at ground level in the centre) was protected by a propolis wall escaped destruction.

Colony 1 prior to the fire.

Fig. 3c. Colony 1 prior to the fire protected from the elements by the growth of vegetation around it.

Fig. 3b. The nest of Colony 1 whose 14 combs had been protected from the fire by a propolis wall that covered the cavity.

Fig. 3b. The nest of Colony 1 whose 14 combs had been protected from the fire by a propolis wall that covered the cavity.

Fig. 3c. Colony 1 prior to the fire.

The nest of colony 1 prior to the fire.

Colony 2 (Fig. 4a) appeared to have been severely affected by the fire, which judging from the numerous rocks about the entrance that were cracked (Fig. 4b), the heat was intense. The propolis wall had melted and the combs had melted except for the comb mid-rib (Fig. 4c). During the examination of the colony in cold windy weather, two bees emerged but were unable to depart normally on flights as if both were too cold and starved to do so. However, on the following sunny day foraging activity was witnessed (Fig. 4d).

IMG_0046

Fig. 4a. Colony 2 is located to the right side of the foremost boulder below where the orange lichens start.

Colony 2 prior to the fire.

Colony 2 prior to the fire.

4b. Rocks around the entrance to the nest cracked from the heat of the fire.

4b. Rocks around the entrance to the nest cracked from the heat of the fire.

Fig. 4c. The almost deserted combs of Colony 2.

Fig. 4c. The almost deserted combs of Colony 2.

Fig. 4d. Foraging activity at Colony 2.

Fig. 4d. Foraging activity at Colony 2.

From inspection, Colony 3 (Fig. 5a) had a propolis wall which enclosed the entire nest but which was melted by the fire – as had some of the combs which consisted only of the comb mid-rib (Fig. 5b). On a subsequent visit, of the seven combs that were visible, the bees were clustered on the end three combs but were still actively foraging (Fig. 5c).

Figure 5a. The entrance to Colony 3 lies under the boulder with a seemingly horizontal crack in it and to the right of the reddish, lichen covered rocks (situated bottom left in the picture).

Figure 5a. The entrance to Colony 3 lies under the boulder with a seemingly horizontal crack in it and to the right of the reddish, lichen covered rocks (situated bottom left corner in the picture).

Colony 3 prior to the fire.

Colony 3 prior to the fire.

Fig. 5b. Bees of Colony 3 clustered on some melted combs. Note the remains of the melted propolis that once encased the nest entrance.

Fig. 5b. Bees of Colony 3 clustered on some melted combs. Note the remains of the melted propolis that once encased the nest entrance.

Fig. 5c. Bees of Colony 3 clustered on some combs while the others are deserted.

Fig. 5c. Bees of Colony 3 clustered on some combs while the others are deserted.

Propolis and beeswax: It has been recorded that during the heat from a fire, bees keep the colony ventilated by vigorously fanning their wings to prevent the combs from melting (Root 1950). At temperatures of 25-45°C propolis is soft and pliable and most varieties will melt between 60-70°C and some only at 100°C. Beeswax melts at about 63°C. Honeybees maintain a hive temperature of 34°C within the brood area. Propolis is a mixture of different plant resins and gums collected from unopened flower buds, especially of Leucospermum and Protea species within Cape Point. Because it consists of the defensive chemical exudates of plants, it has many anti-bacterial and anti-fungal properties and is aromatic. The major components of propolis are resins (45-55%); waxes and fatty acids from both beeswax and plants (25-35%); essential oils (10%); protein – mainly pollen (5%); and trace elements – mainly iron and zinc (5%). Propolis used within the hive may have beeswax added to it to be more pliable but can also consist of pure plant exudates in outer structures. Its thickness depends on the purpose of the structure under construction. In the case of the colony which survived the fire, the propolis wall (pro = before; polis = the city) built at right angles to the combs, did indeed protect the nest. It appears that the main function of the propolis barrier was the exclusion of rain and cold. Propolis has many uses in that it can be used to control ventilation, waterproof the interior of a nest, to control temperature and humidity within the nest, and to exclude various pests from entering and hiding within the nest. The prolific use of propolis by the African honeybee may also be as a result of attempts to deny hiding places within the hive to the small hive beetle (Aethina tumida) by sealing crevices. Natural nests are often located in cavities which afford many hiding places to the small hive beetle, thus lining the cavity with propolis effectively seals the nest off from its immediate surroundings (Tribe 2000). The extent to which propolis may be used to insulate a nest was illustrated in the complete enclosure of combs hanging from under a branch of a tree in Pretoria, allowing bees to forage from just a few small openings in the propolis sheath (Tribe & Fletcher 1977).

Cape Point Nature Reserve: Unlike the summer rainfall honeybee race (Apis mellifera scutellata) of southern Africa, the Cape bee nests are more often located within shrubbery at ground level. This does not preclude them from constructing nests in elevated places like those for A. m. scutellata. In fact, in suburbs of Cape Town, Cape bee nests have been located several meters high in exotic palm and pine trees. Data on Cape bee nesting sites recorded in Cape Point thus far indicate that about 90% of selected sites are located under or within rock crevices (Fig. 6).

Figure 6. Colony in the cliff face at Cape Point Nature Reserve.

Because honeybees will reoccupy any site previously inhabited by other honeybees, it is likely that many of these sites have been in use for centuries. What was amazing was that bees often issued in a steady stream from a relatively small hole in the soil at the base of a rock at some of these nests. How were these bees able to locate such hidden nesting sites which must occupy a substantial cavity size below the rock of say, about 42 litres – which is the capacity of a Langstroth hive? It is probable that such nesting sites were located by scouts in the past when they were more exposed, possibly as a result of a fire followed by winds and then heavy rainfall which revealed the cavity under the rock. With an average fire frequency of 15 years, the debris and plant growth during this time around the site could have closed off most of the cavity, the bees maintaining only the narrowed entrance.

Are nesting sites a limiting factor? Is the availability of nesting sites a limiting factor on the number of colonies able to reside in Cape Point? This is difficult to answer without knowing how many reproductive swarms are issued each year from the established swarms.

Fig. 7. Swarm of Cape bees during the canola flow at Caledon

Fig. 7. Swarm of Cape bees during the canola flow at Caledon

An individual colony may issue none or several reproductive swarms a year (Fig. 7) – largely determined by the capacity to expand within the nesting space (i.e. over-crowding), the strength of the colony (nectar and pollen reserves) and the vigour of the queen. Usually the old queen departs with flight-experienced workers, leaving behind several queen cells from which virgin queens will shortly emerge. If the colony is still over crowded, one or more additional swarms may leave with virgin queens – but this is more common among A. m. scutellata. However, at least one swarm at Cape Point was unable to find a secure nest and built their combs from interlacing branches within a fynbos thicket. Any approach to this nest elicits an immediate hostile reaction, presumably because of the odour of crushed vegetation underfoot. In the event of a fire, this colony would be incinerated.

Abscond? What remains to be seen is whether the three colonies which escaped the fire will remain where they are or will abscond. The Cape Point fire was extinguished and foraging still exists outside the burnt swathe, although the foragers will have further to fly. In the past similar wild fires would burn over a vast area, leaving little or no forage for many weeks. For example, a wild fire in the Cedarberg burnt for six days and covered 13 500ha (Jarman 1982) turning the entire area into a wasteland for bees with no forage. However, the resilience of the fynbos was revealed at Cape Point in the appearance of fire-asparagus (Asparagus lignosus) shortly after the fire which began flowering within weeks – to the benefit of the numerous bees visiting it. Also emerged in response to the fire were Haemanthus sanguineus and a smattering of plants such as Oxalis which were also visited by foragers.

Honeybee predators: Cape Point Nature Reserve no longer has honey badgers (Mellivora capensis) which possibly occurred there in the past, thereby eliminating one of the honeybees’ most destructive enemies. Had they been present, there would be the annihilation of those colonies accessible to them, followed by the later re-establishment by reproductive swarms from other areas within the park – thus creating an on-going dynamic. Although baboons also readily raid honeybee nests and are prevalent in the reserve, none of the 31 colonies has thus far been raided by baboons.

The Authors at work:

References

Jarman, M. 1982. A look at the littlest floral kingdom. Scientiae 23(3): 9-19.

Johannsmeier, M.F. (Ed.). 2001. Beekeeping in South Africa. Plant Protection Research Institute Handbook No 14, Agricultural Research Council of South Africa. 228pp.

Root, A.I. 1950. The ABC and XYZ of Bee Culture. The A.I. Root Company, Medina, Ohio, U.S.A. 703pp.

Tribe, G.D. 2000. A migrating swarm of small hive beetles (Aethina tumida Murray). South African Bee Journal 72(3): 121-122.

Tribe, G.D. & Fletcher, D.J.C. 1977. A propolized nest in the open. South African Bee Journal 49(4): 5-7.

Acknowledgment: The permission granted by SANParks to locate and analyse the nesting sites of honeybees in the Table Mountain National Park is gratefully acknowledged.

 

 

Restio Species as a Source of Pollen in Autumn in the Fynbos

By Geoff Tribe

IMG_4061 - Version 2

The cavity dwelling Western Honeybee inhabiting temperate regions relies on its honey stores to tide it over the seasonal dearth periods which is a feature of its natural environment. The fact that they live in cavities allows ample stores to be accumulated for this purpose. It is this behaviour of hoarding surplus honey that is exploited by commercial beekeepers to their advantage by migrating hives from one honey-flow of exotic crops to the next. In the summer rainfall highland areas a typical seasonal cycle may start with the Highveld gums (a variety of Eucalyptus species) in spring, then on to sunflowers, soya beans, Eucalyptus grandis plantations, and finally to the Aloe greatheadii var. davyana honey-flow in winter. The seasonal dearth period for the Cape bee (Apis mellifera capensis) which inhabits the winter rainfall region of South Africa occurs during the summer months from January to March when few indigenous plants are in flower under a hot cloudless sky. Yet the honeybees survive, albeit in some areas with the help of exotic plants, the most valuable being several Australian Eucalyptus species.

075 Fig. 1

Fig. 1. A view of DanielsHoogte Private Reserve nestled on the top of Aurora Mountain 800m above sea level.

An exploration of the mountain (Fig. 1) above the West Coast town of Aurora in the first week of May 2015 revealed an abundant but unexpected source of pollen for Cape honeybees in the form of a Cape reed species belonging to the Restionaceae family. Fynbos vegetation is distinguished by its constant association with these tufted reeds which have been used to provide thatching material from the time of early European settlement. In the summer rainfall regions the Restionaceae are replaced with grasses. Restio species are usually dioecious with male spikelets drooping and female spikelets erect and are wind pollinated.

The fynbos covered Aurora Mountain is surrounded below in the Sandveld by potato and wheat fields and is contiguous with the Piketberg Mountain. The mountain fynbos here comprises of at least five species of Restionaceae and five Protea species of which Protea laurifolia (fig. 2) and Protea nitida (Fig. 3) were in flower.

046 Fig. 3

Figure 3. Many insects including honeybees visited the flowers of Protea nitida.

One species of Bruniaceae (Fig. 4) had just begun to flower as a result of the heavy coastal fog which envelops the mountain in the early morning (Fig. 5). However, around the farmhouses (32° 41’ 04’’S 18° 32’ 10’’E) were some ancient Eucalyptus globulus trees which were in flower. A commercial beekeeper had placed hives (Fig. 6) in groups of three at four localities within the fynbos vegetation. They were placed on recycled plastic containers filled with sand and strapped down to prevent the honey badger from accessing them – the mountain still inhabited by leopards, lynxes, mongooses, and various antelope including klipspringers and exotic fallow deer.

Figure 5. The morning coastal fog seen through the ‘vensterklip’ which can completely envelope the mountain.

Figure 5. The morning coastal fog seen through the ‘vensterklip’ which can completely envelope the mountain.

Figure 6. Beehive placed on top of a sand-filled container and strapped down to prevent access by the honey badger.

Figure 6. Beehive placed on top of a sand-filled container and strapped down to prevent access by the honey badger.

At this time of year the fynbos was drab and the prickly undergrowth showed very few natural resources on which the bees could forage. During the hikes around the outer rim of the mountain, no natural honeybee nests were discovered – not even in the 17 aardvark holes that were inspected. However, in several small secluded valleys there was a Restio species, Elegia tectorum, growing in thick clumps which reached to one’s elbows and which released clouds of pale yellow pollen as one pushed through it. It was here that the bees were encountered in large numbers collecting pollen (Fig. 7).Only pollen collectors were observed. No bees were visiting the female flowers (Fig. 8). It was observed that pollen was not available early in the morning, especially not until the mist had lifted, but became available only during the hotter part of the afternoon when the inflorescences were dry.

Figure 7. A honeybee collecting pollen from male Elegia tectorum flowers.

Figure 7. A honeybee collecting pollen from male Elegia tectorum flowers.

Figure 8. Female Elegia tectorum flowers not visited by honeybees.

Figure 8. Female Elegia tectorum flowers not visited by honeybees.

Elegia tectorum, or Cape thatching reed (as its name tectorum = ‘roofing’ implies), may grow to over 3m in height and occurs naturally in marshes and seeps on deep sand from Clanwilliam to Port Elizabeth. Male and female flowers occur on separate plants; the flowers are small and borne in compound branched inflorescences and flower in autumn (from March to April) which lasts for about four weeks. Large areas of several metres in diameter of either just male or female plants were observed on Aurora Mountain in close proximity to each other. Small black seeds are produced with smoke greatly increasing their germination rate.

Honeybees will be found in even the most desolate desert areas throughout southern Africa in which they find the means to survive. Within the mountain fynbos of the West Coast, restios appear to play an important, if unacknowledged, role in supplying pollen to honeybees at a time of year when such resources are in short supply. More than 400 species in about 40 genera of the Restionaceae family occur in the winter rainfall regions of South Africa and Australia, with outliers in Africa, Madagascar, Indo-China and Chile. There are about 168 restio species in South Africa which are confined mainly to the fynbos biome. They appear to play a far more important role in the ecology of the Cape honeybee than that of a wind pollinated species might warrant.

References

http://www.plantzafrica.com/plantefg/elegiatectorum.htm

127 (2)

A harvester termite nest found at Aurora.

The prehistoric looking 'koringkriek' or corn cricket, Hetrodes pupus, active on the mountain

The prehistoric looking ‘koringkriek’ or corn cricket, Hetrodes pupus, active on the mountain.

The presence of rock art in caves on the mountain indicates that it has been inhabited for many centuries

The presence of rock art in caves on the mountain indicates that it has been inhabited for many centuries.

 

Rock Art Paintings of Honeybee Combs in the Western Cape

By Geoff Tribe

068 fig 6b

Wild honeybee nests in southern Africa have been robbed for millennia by Bushmen (San) who were the original inhabitants of the sub-continent before the arrival of the Bantu tribes from the north and the European settlers from the south. Honey was possibly the only sweetness known to them which was obtained not only from honeybees but also from stingless Trigona bees. Bee brood was also a much relished source of food. Honeybee nests were marked in some way and individually or tribally owned and were robbed at the appropriate season when the combs were full of honey. Being nomadic, the San travelled vast distances following the availability of food according to the seasonal cycle.

There are many thousands of paintings on the walls of caves or rock overhangs in southern Africa which are thousands of years old, with some extending into the early colonial period. The San (Bushman) painters covered a wide variety of subject matter, the interpretation of some of them fill many scholarly books. Honeybees also played an important role in their mythology (e.g. Pager 1974; Lewis-Williams & Dowson 1989).

One painting that occurs in many parts of southern Africa and which was initially thought to depict a necklace was subsequently shown to represent combs of honeybees. Necklaces were worn by the San and were made out of small pieces of ostrich egg shells in which a hole was drilled and then strung together with a piece of string. However, a Zululand commercial beekeeper, Robin Guy, on visiting the preponderance of paintings in the Natal Drakensberg identified these ‘necklaces’ as depicting hanging honeybee combs within a honeybee nest.

Fig. 1

Fig. 1 The hanging combs of a nest of Apis mellifera scutellata hanging under the branch of a pine tree in a suburb of Pretoria.

There is no mistaking their resemblance to the combs of a wild honeybee nest (Fig. 1). This was further confirmed where at some of these sites, the catenary combs were accompanied by dots or bees with red bodies and white wings (Fig. 2a & b).

Frequently the artists made use of the varied surface relief of the walls of the cave to incorporate certain blemishes or imperfections into their paintings. Examples include the painting of an eland around an inclusion in the wall which is used to represent its eye, or a procession of antelope which appear to be emerging from a crack in the wall. The figure of a woman may be painted around a hole in the wall to represent a female’s abdomen or womb (Anderson). In this painting (Fig. 2a) it appears as if the bees are flying out of a crevice in the wall – very much as they would in the wild where many colonies make their nests within rock crevices. The large number of bees, especially concentrated at the lip of the crack and spreading outwards, indicates either an orientation flight or an absconding swarm. Botha’s Shelter contains 899 magnificent paintings including that of combs painted below the stomach of an eland and a bird associated with the bees which in the context could represent a honeyguide (Pager 1971).

Rock art depicting honeybees appears to be rather scarce along the western seaboard of southern Africa as compared with that of the eastern seaboard. And the West Coast paintings most often depict hanging combs which occur in such places as overhangs along the Oorlogskloof Hiking Trail (Fig. 3); on a farm in the Swartruggens Mountains overlooking the Tanqua Karoo (Figs 4 & 5); and in a cave in the Aurora Mountains above the town of that name (Fig. 6). Here again (Fig. 4) the artist has made use of the natural shape of the cave wall to incorporate the convex bump on which to paint the catenary combs. This gives a more realistic three dimensional effect of what a real nest would look like if viewed from below. Similarly, honeybee nests are often found hanging under projecting rocks, and the artist (Fig. 3) has made use of the small projection from the cave wall under which to paint the combs – simulating what occurs in nature.

Rock art depicting the robbing of bee nests occurs more frequently along the eastern seaboard of South Africa. For example, a painting in Eland Cave in the Drakensberg Mountains depicts a honey hunter with a bag on his back climbing a forked ladder to reach a honeybee nest around which bees are flying in agitation (Pager 1973). Similarly, three bees’ nests with ladders giving access to them may be seen in Anchor Shelter (Crane 1983). Near Bergville in KwaZulu-Natal, there is a ladder in close association with two bees’ nests depicted in a painting in Tugela Shelter (Crane 1983). In the Brandberg Mountains of Namibia a swarm of 376 bees are depicted in a painting. Yet the only depiction of a honey hunter in the Western Cape appears to be in a high overhang on a farm near De Hoek at the foot of the Swartbergpas 10km from the Cango Caves in the Oudtshoorn District. In this now faded painting, a man appears to be lowered from above with both hands gripping the rope above him and dots, presumably bees, all around his head. Attached to his body is what appears to be a flaming torch. In this ‘cave’, known as Buck krantz, because it also depicts antelope plummeting over the cliff, there are several honeybee nests in its walls even to this day. These nests are in holes in the wall which are entirely covered with propolis except for several tiny entrances through which the bees forage (Fig. 7).

Fig. 7

Fig. 7 Propolis covered entrances to honeybee nest in cavities in the wall of the Buck krantz rock overhang where a painting depicts the robbing of these same nests.

Also in the Klein Karoo is a painting of a swarm of bees amongst a group of dancing figures – the droning in the ears when in an altered state during a trance dance is recognised as the potent humming of bees (Rust & Van der Poll 2011). Here the bees are again depicted with red abdomens and white wings.

Why honeybees and robbing activity in rock art is more frequently encountered along the eastern seaboard could be because of a variety of reasons. Possibly the most important difference is that the eastern seaboard is much wetter and more rugged and thus honeybees are more prolific with many more and varied nesting sites available. In contrast, the fynbos and succulent Karoo of the western seaboard is far drier, with most honeybee nests located in outcrops of rocks or in the ground. At Buck krantz the depicted scene of the honey hunting can easily be visualized as occurring in the overhang – as with the antelope being chased over the cliff above the ‘cave’, but do single depictions of combs in the other caves, not always associated with other paintings, indicate a nest nearby and its ownership?

Selected references:

Anderson, G. (no date). Bushman Rock Art: South Africa. Art Publishers. 64pp.

Crane E. 1983. The Archaeology of Beekeeping. Duckworth, London. 360pp.

Crane, E. 2005. The rock art of honey hunters. Bee World 86(1): 11-13.

Guy, R.D. 1972. The honey hunters of southern Africa. Bee World 53(4): 159-166.

Lewis-Williams, D & Dowson, D. 1989. Images of power: understanding Bushman rock art. Johannesburg: Southern Book Publishers.

Pager, H. 1971. Ndedema. Akademische Druck- u. Verlagsanstalt, Graz/Austria. 375pp.

Pager, H. 1973. Rock paintings in southern Africa showing bees and honey hunting. Bee World 54(2):   61-68.

Pager, H. 1974. The magico-religious importance of bees and honey for the rock painters and Bushmen of southern Africa. South African Bee Journal 46(6): 6-9.

Rust, R. & Van der Poll, J. 2011. Water, Stone and Legend: Rock Art of the Klein Karoo. Struik. 128pp.

Tribe, G.D. 2000. A Bushman painting of a honey-hunter in an Oudtshoorn cave which still contains honeybee nests in its walls. South African Bee Journal 72(2): 84-87.

Woodhouse, B. 1984. When Animals were People: A-Z of Animals of Southern Africa as the Bushmen saw and thought of them and as the camera sees them today. Chris van Rensburg Publications. 120pp.

Dr Geoff Tribe

Dr Geoff Tribe

Why do honeybees react the way they do to smoke?

By Geoff Tribe (after a discussion on smoke with Jenny Cullinan and Karin Sternberg)

Fire at Cape Point Nature Reserve

The 11km fire at the Cape of Good Hope Nature Reserve, March 2015

While viewing the aftermath of the recent fire that cut a swath of devastation through Cape Point Nature Reserve before it was extinguished, we wondered whether any of the wild swarms we were monitoring there had survived the blaze.

after the fire 1 after the fire 2, The question then arose as to what benefit the innate behaviour of imbibing honey in the presence of smoke could be? How did it contribute to the survival of a swarm whose nesting site is enveloped in fire?

The adage that it is better to work honeybees with a smoker and without protective clothing than vice versa is easily confirmed in practice. The earliest record of the use of smoke to control honeybees is from a tomb painting in Egypt from c. 1450 BC where a kneeling beekeeper is removing combs from the back of a stack of horizontal hives, while smoke was used to drive the bees off these combs towards the flight entrance at the front (Crane, 1999). The use of smoke to subdue honeybees has obviously been known for millennia, because a hieroglyph of the honeybee was part of the titular of the King of Egypt from 3100 BC, the honeybee being of importance in Egypt long before this time. But why should the bees behave the way that they do in the presence of smoke unless it had evolutionary benefits? Various materials may be used in a smoker to subdue honeybees, each beekeeper vouching for the merits of the material that he uses in calming the bees. These may include burlap sacks, dry pine needles and dry herbivore dung – all of which have the same effect on the bees despite what material is used as fuel. Historical records show that dagga was used by the Khoesan (Quena) to smoke the bees but without any comment on any added effects that it may have had on them!

Smoke consists of many compounds, and since all fuels are equally successful in subduing honeybees on whatever continent, they are possibly reacting only to one or more of the chemical components of smoke. These components are as yet unknown, and neither are the receptor sites on the bee where this recognition is facilitated. Another suggestion is that the receptors of the honeybees are reacting to a certain size of smoke particle.

What is not disputed is that smoke causes honeybees to imbibe honey and with their distended abdomens they are less inclined to sting. Honeybees have first to grip the target before the sting can be brought into play by bending the abdomen, a distended abdomen making this procedure more difficult. Smoke also disrupts the chemical communication of the bees. Bees protect their valuable honey stores from mammals by a concentrated mass attack on the intruder after it has been marked by a guard bee whose stinging apparatus is ripped out and the alarm pheromone is released in quantity. Hence the practise by beekeepers of smoking the area that has been stung to smother the odour and to confuse the bees. The Western honeybee (Apis mellifera) inhabits temperate areas which are subject to regular fires which are part of their ecology. Savannah grasslands and fynbos need fire to survive as such.

Honeybees however are unable to escape fire by flight as witnessed by entire apiaries being burnt to cinders and all swarms perishing. Honeybees only react to smoke if it wafts into their hive, which gives them little warning of impending disaster. Observation hive studies have shown that honeybees which abscond do so after consensus has been reached within the hive – which takes many days. By overcrowding an observation hive with bees it is possible to force the swarm to abscond. As the bees prepare to abscond, perhaps six dances indicating six potential nesting sites may occur initially. Over a few days this number is narrowed down to one dance and consensus has been reached. The swarm leaves the hive after the number of vibratory dances (an inhibitory dance where one worker places its head on another and shakes it by a dorso-ventral abdominal movement) (Fletcher, 1978) per unit time reaches zero. exposed nestThere would not be time to organise a mass evacuation of the hive in the event of a fire. In any case, smoke would disrupt all chemical signals involved in coordinating swarming and absconding. Exposed wild colonies would perish , the selection of secure nesting sites in fire-prone vegetation thus having primary survival value.

Nest under a rock

A wild nest deep under a rock

Laying queens would be unable to leave with a swarm escaping a fire because she would be too heavy to fly and, like the workers, would not be inclined to desert her brood. A swarm preparing to swarm or abscond first starves their queen and prevents her from laying eggs by not preparing cells for her in which to lay eggs. Absconding occurs soon after most young bees have emerged from their cells and the stores have been consumed – except that which is needed to establish the swarm at the new nesting site and is carried in the bees’ stomachs. This preparation again takes several days. Absconding usually takes place when conditions are adverse and there is an ‘awareness’ of this throughout the hive due to the ‘feedback’ mechanism in operation within the hive, where for example, the lack of incoming food causes a reduction or cessation in egg-laying.

Honeybees are therefore unable to escape by absconding in the face of the fire and exposed colonies would perish. The innate behaviour of honeybees to smoke must thus have become entrenched in those swarms which did survive the fire. The bees are therefore not trying to escape the fire by fleeing – so what is the value of imbibing honey? The value appears to be in the survival of those swarms which escaped the initial fire.

Natural fires in southern Africa in days of yore would burn over a vast area. For example, the fire that started in Riviersonderend in February 1869 that was driven by a hot Berg wind burnt the indigenous forest all the way from Swellendam to Humansdorp, driving elephants and other game into the sea for refuge. Swarms surviving such fires would emerge to find a ‘lunar’ landscape devoid of plants to sustain them and thus would be forced to abscond. Smoke causes bees to imbibe honey and retreat to the far recesses of the nest cavity. Bees will imbibe any honey flowing from melted combs and so function as living storage units. Under such conditions, to sting and die would cause the loss of this crucial honey store. Hence also a reason why they are then less inclined to sting. It appears that the innate behaviour of honeybees to imbibe honey in the presence of smoke has survival value in that it allows the eventual escape by migrating from a devastated landscape after the fire has passed. The honey stored in the bodies of the bees would allow the bees to survive the initial calamity and then to organise a migration out of the area and rebuild comb in the new nest site. This behaviour has become innate, which presupposes that the Western honeybees (and Apis species in general) have been subjected to fire for many millennia and have evolved to survive it.

The Heuningberg

The Heuningberg in the foreground dwarfed by the Groot Winterhoekberge behind them

A natural indication of the value in imbibing honey was recorded by O.F. Mentzel in 1787 at the Heuningberg (Fig. 4) where honey was bartered with the Khoesan. The translation records: “A few miles towards the east lie the Honig Bergen. These derive their peculiar name from the bees which find abundant nourishment in the many wild flowers and store their harvest in the crevices of the rocks. The Hottentots clamber up these mountains…to look for honey which they discover the sooner because the sun often makes it fluid, so that it runs onto the rocks, is again collected by the bees and carried back but in this way the storerooms are soon discovered”(Tribe, 1996). Temperatures in summer in this region exceed 40°C and the rock faces are blisteringly hot. Here the bees’ reaction is to heat and the melting of the comb but in the absence of smoke.

Do other organisms have innate reactions to fire? There appears to be none with the same innate response as that of honeybees. Various predatory birds are attracted to fire to capture escaping insects and rodents, but smoke is just a learned signal indicating a meal.

Anyone who has tried to remove a nest of the alien European wasp (Vespula germanica) which has invaded the fynbos and which forms massive multi-queen colonies because the African climate is so conducive to them, will rue the fact that they do not respond to smoke as do honeybees. The mass attack by these wasps soon results in the veil becoming completely covered in wasps with stingers extended and the odour from their stings becoming overpowering. With no response to smoke such as retreating from it, presumably because they nest in the soil and are not unduly affected by fires, they have no comparable reaction to that of honeybees. Even so, there is no honey stored in the wasps’ nests, their brood being fed progressively with regurgitated protein from soft bodied insects killed by their foragers.

The innate behaviour of honeybees to smoke has allowed people to effectively control them, making modern beekeeping including the movement of hives to pollinate crops possible.

survival

Crane, E. 1999. Recent research on the world history of beekeeping. Bee World 80 (4): 174-186.

Fletcher, D.J.C. 1978. Vibration of queen cells by worker honeybees and its relation to the issue of swarms with virgin queens. Journal of Apicultural Research 17(1): 14-26.

Tribe, G.D. 1996. Heuningberg: past and present. South African Bee Journal 68(2): 39-47.

Images by Geoff Tribe, Jenny Cullinan and Karin Sternberg

 

Leafcutter Bees of the Tribe MEGACHILINI

By Geoff Tribe (Images by Jenny Cullinan and Karin Sternberg)

leafcutter bee 8

Megachile frontalis (Identified by Dr Connal Eardley, National Collection of Insects, Pretoria)

This large and abundant tribe known generally as leafcutter bees, even though nests may be lined with various materials besides leaves, is found in every continent where the majority of the species belonging to this tribe are solitary. Unlike other solitary or sub-social bee groups, secreted cell linings are absent. Material for cell walls and linings is instead brought in from outside and, depending on the species, includes pieces of leaves, chewed leaf material, resin, mud, or pebbles.

The distinguishing feature of the family Megachilidae is that the females of non-parasitic species carry pollen by means of a scopa on the venter of the abdomen instead of on the hind legs. The following genera are included in the Megachilini: Chalicodoma, Chelostoma, Heriades, Hoplitis, Megachile and Osmia.

Leafcutter bees in southern Africa are stoutly built, brown or black bees up to the size of a honeybee, hairy and with a conspicuous yellow tuft of hairs on the underside of the abdomen where the pollen grains are collected on this special apparatus. The female leafcutter bee seeks out a tube or tunnel that is of the correct dimensions which is dry and sheltered. Such cavities include hollow stems, holes in a wall, deserted cavities constructed by wood-boring beetles and even man-made holes in buildings.

leafcutter bee 4 leafcutter bee 5

The female Megachile venusta cuts a fairly thin oval piece of leaf from a smooth-leaved plant and carries it between her forelegs to the selected nesting site. The leaf segment is pressed into position with her head at the base of the tube. This process is repeated until both the base and walls are lined with overlapping leaf segments. The first small cup about 10mm deep is then filled to three-quarters with a yellow paste of pollen and honey. On this she lays a single egg before sealing the cup with leaf segments and then repeats the process with one cell on top of the other until the tube is filled with such cup cells containing brood. Finally the entrance is stuffed with assorted pieces of leaf of different shapes and sizes before being sealed with a plug of chewed leaf cemented with saliva. There appears to be just one generation per year.

The fully grown larva spins a cocoon which lines the inside of the cell and after excreting, coats the inside with the excrement which dries to form a water-proof varnish. Here it remains for several months until the following season, after which it pupates and emerges two or three weeks later.

A number of the Megachilidae have become ‘cuckoo’ bees where they lay their eggs in the nests of related bees, their larvae feeding on the honey and pollen paste stored by the host which results in the starvation of the host larva.

The related tribe of Anthidiini is much smaller and less abundant than the Megachilini and use the same materials as above for lining their nests except for mud. Genera include: Anthidium, Trachusa, and those with Anthidium as the root. The communal carder bees (Immanthidium) are included here. As their name implies, various cottony fibres which they strip from hairy plants are used to construct the nest. One such carder bee nest made out of a cottony material and the size of a fist was discovered in the hills above Pietermaritzburg in 1972 built within a huge discarded concrete water pipe. Here it was protected from rainfall and the entrance hole to this mass of ‘cotton’ was streaked with yellow pollen. Inside were several individual cells provisioned with a honey and pollen paste.

References:

Michener, C.D. 1974. The Social Behavior of the Bees. Belknap Press, Massachusetts, 404pp.

Skaife, S.H. 1979. African Insect Life. Struik, Cape Town, 279pp

leafcutter bee 2 leafcutter bee 6 leafcutter bee 7 leafcutter bee 1

 The Author…

Geoff Tribe

Geoff Tribe

Getting the shots…

at the beach

Jenny Cullinan

bee paradise

Karin Sternberg

Solitary Anthophorid bees

By Geoff Tribe (Images by Jenny Cullinan and Karin Sternberg)

Anthophorid 1

There are over 100 species of bees in southern Africa belonging to the family Anthophoridae which has a world-wide distribution. Anthophorid bees generally resemble the basic stout form of small carpenter bees but with abdomens that are usually striped in shades of black and grey. The flight of these hairy bees is fast and erratic and accompanied by a shrill hum. All African species nest in the soil, usually in sandy banks where they construct a deep central burrow from which leads short side burrows that end in cell chambers in which their brood is reared. The female bee provisions the brood cells which are lined with a wax-like material with a mixture of nectar and pollen, onto which she lays an egg. Some species construct an entrance made of soil particles cemented together with saliva which projects from the soil.
Males of many anthophorid species have antennae that are unusually long and thus anthophorids may also be known as ‘long-horned bees’. One species found in the Cape Peninsula closely resembles the dark Cape bee (Apis mellifera capensis) except for its longer antennae and slightly smaller size. digger bee 3Males of anthophorids may form ‘sleeping clusters’ where they congregate by attaching themselves to a twig within a bush by means of their large mandibles. One such cluster consisting of 68 males of the same species was located one evening after the sun had set in the Natal Drakensberg near Cathedral Peak forestry station in about 1986.
A large number of anthophorids are known as ‘cuckoo bees’ but their behaviour is not that of true parasites. This cleptoparasitism is widespread in the Anthophoridae and related families where the female enters a brood cell already provisioned by a host female and lays an egg of her own. The ‘cuckoo’ females lay an egg on the accumulated larval provisions of other bee species instead of provisioning their own nests. The egg or young larva of the host bee is either killed directly by the female cuckoo or killed by the ‘cuckoo’ larva. One such ‘cuckoo’ species found commonly in the south-western Cape is Thyreus delumbatus which ‘parasitizes’ Anthophora and Amegilla bees where they enter their nests to deposit their eggs. This ‘cuckoo’ bee is slightly smaller than a honeybee and has a ‘fish-bone’ pattern in black on its otherwise powder-blue body.
There are also cuckoo wasps such as the bright metallic green Stilbum cyanurum which lay eggs in nests of solitary wasps and bees, their larvae also feeding on the host’s provisions or larvae. These cuckoo wasps are extremely hard and strongly sculptured to withstand attack by the hosts, and are able to roll up into a ball in self-defence.

digger bee 4 Digger bee 1Anthophorid 5 Anthophorid 4 Anthophorid 3 Anthophorid 2digger bee 6 digger bee 5

Sub-Social Allodapine Bees

By Geoff Tribe (Images by Jenny Cullinan and Karin Sternberg)

There are many other species of indigenous bees in southern Africa besides the ubiquitous honeybee Apis mellifera which is today essential for the pollination of many introduced food crops. The large carpenter bee (Xylocopidae) which fills the same niche in southern Africa as the bumble bee does in Europe is fairly obvious as it flies about trees in flower such as the keurboom (Virgilia oroboides). Yet there are many other species of much smaller solitary or sub-social bees that play an important role in the pollination of indigenous vegetation. One such interesting group of bees belong to the Allodape and closely related genera which are generally referred to as ‘allodapine bees’ to distinguish them from members of the genus Ceratina or lesser carpenter bees. Allodapines are found in Asia and Australia but are most abundant and diversified in Africa south of the Sahara. What distinguishes them from other such bees is that they have no partitioning cells in their nests and brood is reared in a single burrow and the larvae are fed progressively with small amounts of nectar and pollen made into a paste.

Allodapine bees are usually brown or black with the largest species about 15mm long, but they all have yellowish facial markings either as thin lines or a patch in the lower centre of the face.

Allodapine on flower Allodapine hiding

They construct their nests in hollow or pithy dead stems, especially where the stems have been broken or burnt to expose the pith. The abundance of nesting sites has a great influence on populations of allodapines and large numbers are able to build up in areas where there are regular nesting sites. Large numbers of allodapine bee nests could, for example, be found in dead khakiebos (Amsinckia calycina) stems alongside railway tracks in KwaZulu-Natal in the 1970’s. Khakiebos was accidentally introduced into South Africa from Chile in fodder purchased for horse feed during the Anglo-Boer War and the weed followed wherever the British mounted troops went. The practice was to spray herbicide on either side of the railway lines to prevent the encroachment of weeds onto the tracks, and this often caught fire and so formed an ideal nesting site for these bees. A small trial showed that a major limiting factor was the number of broken khakiebos stems available for nesting. The number of nests could be greatly increased with the artificial cutting of unbroken stems, so creating access to the pith. Dry flower stalks of Aloe, Watsonia, Gladiolus, Aristea or even the exposed ends of grass thatch of roofs are also used for nesting. This can be observed in the thatch roofs of many chalets in game reserves in South Africa.

Within the allodapines there is much variation in behaviour between species with an intergradation from purely sub-social forms, to semi-social, or primitively eusocial colonies. Sub-social associations consist of one female and her progeny. Eusocial is where there is a reproductive division of labour where the worker caste cares for the young of the reproductive caste and there is also an overlap in generations so that offspring assist parents.

Allodapine on Wimmerella secunda Allodapine on Rootthug

A typical case study of allodapine ecology is that of the eusocial Allodape angulate by S.H. Skaife in the Cape Peninsula. In the winter rainfall region of South Africa adults of the new generation emerge in the middle of summer (end December to February) but remain largely quiescent through the remainder of summer and then disperse in autumn to found new nests. Breeding takes place in July and August and the solitary females begin new colonies. After removing the pith of a broken stem and constructing a burrow, the adult allodapine female usually modifies the entrance to the stem by restricting it by building a collar of chewed pith to fit her size. This nest is then defended either with her head or with her tail end which contains a powerful sting.

Allodapine tail end protecting nest An Allodapine hole

The nests of allodapines do not have partitions like those of many other genera in the Xylocopidae, but larvae of different stages of development are reared together in the same tunnel. Several eggs are laid at the bottom of the tunnel which may be as deep as 14 mm and on hatching the female collects nectar and pollen which she forms into a paste. This she places near the head of the larva, and as it develops it is fed progressively. As more eggs are laid, the larvae are re-arranged in the tunnel with the oldest nearest the entrance. Excrement is systematically removed and the tunnel may become stained with pollen. Pupation takes place in November – there being no pupal cocoon, with the pupa merely lying loose near the entrance. Development from hatching egg to adult takes 14 to 15 weeks. When her progeny, both males and females, become adults, some may leave to form their own nests but a few females remain with the old female while assisting in the rearing of the young. Hence the term ‘sub-social’ for the assembly of the old female with about four female progeny over several months. There are many variations on the above nesting behaviour according to the species involved.

Allodapines can be induced to nest in artificial drinking straws or in a bunch of broken pithy stems of a plant with diameters of less than 10mm tied together in a bundle and attached to a peg in the ground. Such bundles of nests can then be moved to a shady and dry place where they may be monitored. Some bees can be induced to nest in clear straws kept in shade and out of direct sunlight where they may be viewed in situ.

Allodapine markings Allodapine on a daisy

Allodapines are usually observed on flowers consisting of a multitude of small flowers on one head where the pollen is found readily on the surface. Such flowers are less regularly visited by the larger honeybees and carpenter bees and are invariably yellow. An example of such a flower is Cotula coronopifilia or ‘gansgras’ (Asteraceae).

Selected references:

Michener, C.D. 1974. The Social Behaviour of the Bees. The Belknap Press. 404pp.

Skaife, S.H. 1979. African Insect Life. C. Struik Publishers. 279pp.

Wilson, E.O. 1979. The Insect Societies. The Belknap Press. 548pp

 

Queen loss in the Cape honeybee

 

Queenless fighting

When a capensis colony loses her queen, the older bees start attacking the younger, predominantly fuzzy, bees. Chattiing to Dr Geoff Tribe about this phenomenon, Geoff revealed that in about 75% of the time this is what’s happening because the younger bees still have pharangeal glands that can produce protein, and so they can more readily develop their ovaries to lay eggs. What we observed, is that these bees being attacked become submissive, but try to scoot away if they get the chance. Geoff’s theory, and it’s an interesting one, is that the other 25% who become laying workers in the older age group, lay only drone eggs. What is happening with all the fighting and killing going on in the capensis colony, is that the older bees are responding to too much queen pheromone in the hive and need to eliminate the excess queens. But they find workers who are producing queen pheromone to a greater or lesser degree. They pull around and harass those with low amounts, and then sting those with larger amounts. Reading through various research done on Cape honeybee behaviour, those bees with larger amounts of queen pheromone are often the 8 day old bees. The bees which eventually become the laying workers are those which were able to evade the ‘aggressors’ and become pseudo-queens whose pheromone level is as high as that of a queen and are able then to repel these aggressors chemically who then form a ‘court’ around her. During this phase of fighting, which can last several days, one can hear a high-pitched ‘piping’ of the victims in distress.

In a capensis colony, potential laying workers are ready to fully develop the moment the queen is lost. The more ‘capensis‘ it is, the faster they requeen and the lower the slaughter. Construction of emergency queen cells can begin immediately. They build a queen cell around a 2 to 3 day old egg laid by the lost queen and rear it on royal jelly until it emerges as a queen. The Cape bee under such circumstances only rears two or three queen cells, whereas scutellata may have 40 emergency queen cells on one frame – usually in rows at the bottom of the comb.

If the colony is completely queenless and has no eggs from which an emergency queen can be reared, the laying workers will take over. Once there are ‘functional laying workers’ in the hive the bees will begin constructing one or two queen cup cells. These are highly attractive to laying workers – Geoff, in his research, counted 64 eggs in one and they were filled up again the next day – and from an egg laid by a laying worker in this cup, a queen will be reared, will leave on a mating flight and will return to lay eggs as normal.