Tag Archives: wild honeybees

Bombardier Beetles and the Cape Honeybee

By Karin Sternberg    Photographs by Jenny Cullinan and Karin Sternberg (all photographs and videos are protected by copyright)

bee-eating beetle

When people hear the word honeybees, they usually think of bees in boxes and as the source of honey. Little does one know, that there is far more to honeybees than hives and honey. Here in the winter rainfall area of South Africa, the majority of honeybees occur in the wild where nesting sites are selected mainly under rocks or in rock crevices with the physical environment largely determining nesting behaviour. The dominant vegetation is fynbos (heathland) and the Cape honeybee (Apis mellifera capensis) is endemic to this region. The wild honeybees use a prolific amount of propolis to insulate the nest from temperature and humidity fluctuations, which also serves as an effective fire barrier (Tribe et al. 2017). The fynbos vegetation is adapted to fire which is essential for its perpetuation and preservation. An abundance of plant resins and waxes occur within these fynbos plants, largely as chemical defences against herbivory, which offers a diverse and unique source of resins for creating propolis. The propolis wall is therefore also an integral part of the bees‘ immunity with its alchemy of organic compounds offering important antibacterial and anti-fungal properties to the colony. Not only has the Cape honeybee adapted to living in this fire-prone region, but a number of animal species have adapted to living in association with the wild Cape honeybee, such as the Ten-spotted ground beetle, Anthia (Termophilum) decemguttata.

ten-spotted beetle, note-taking

Bees are the most important pollinators of flowering plants worldwide and are ecological keystone species. By co-evolving with angiosperms, bees have contributed decisively to the present phytodiversity and the structure of the terrestrial vegetation and ecosystems (Kuhlmann 2010). The Cape fynbos region is the smallest of the six floral kingdoms in the world, but the most diverse in terms of species’ richness. The existence of a small population of the Ten-spotted ground beetle is partially dependant, too, on the wild honeybee, as observed at a wild honeybee nest in the Table Mountain National Park, Cape of Good Hope Section. Once one starts observing the honeybee in its natural habitat, there is a fascinating array of interconnections waiting to be discovered.

Wild honeybee nest ’93’ located under rock and with a recovery area out of the prevailing SE and NW winds

Wild honeybee nests attract a diverse variety of other creatures, most notably lizards.

All year round we have observed this particular ground beetle on our walks across the Cape Peninsula while tracking honeybees in flight and searching for wild colonies. But, it was only while monitoring this nest that we realised the dependence of the beetle on the honeybee as a source of food. The nest was recently discovered and is at the highest elevation at 190m above sea level of the 93 nesting sites found to date in the Cape Point Section. The nesting site has a south west entrance orientation, with a protected landing area and the colony is deeply recessed under rock with a long and narrow propolis wall, measuring 1100mm (l) by 100mm (h). The nest entrance is surrounded by Metalasia, Syncarpha vestita, Hermas villosa, Restio patens and Diastella divaricata fynbos plants.

The beetle is elongate, roughly 50mm in total length, dull black in colour, has prominent brown eyes, the head is large and flattened and the jaw juts forward to facilitate the capture of prey. It has a reddish-brown heart-shaped thorax, each side marked with a small white spot. The antennae are thin and long and equipped with keen senses of touch and smell. The legs are strong and well suited for running (Scholtz & Holm 1985). The elytra, or wing cases, are sculptured with a number of longitudinal grooves. Each elytron has five spots of white down (The Naturalist’s Library, Vol. 2). They cannot fly as their wing cases (elytra) are fused, forming a strong covering for the abdomen; the membranous wings beneath the wing cases have disappeared (Skaife 1979). The colouration, spots and intensity of the white spots can vary, as we noted when we saw several of these beetles together at this nest location. Being black, they absorb heat which enables them to become active earlier in cold conditions.

A guard bee buzzes the mating pair.

At this particular location we watched as a single beetle warmed up under a rock overhang three metres from the ridge of rocks within which the honeybee colony is located. Between the beetle and the colony were low fynbos shrubs and exposed sandy patches; a controlled burn having taken place in April 2015 in this area. Its abdomen faced into the sun, its head slightly hidden from view under rock. At approximately 10:30am the beetle started moving towards the nest under the protective canopy of fynbos and restiads. At this time we noticed a convergence of at least two other beetles of the same species moving towards the nest. Directly at the nest entrance and in the path of the exiting and returning foragers, slightly hidden from our view by the tufted reed Restio patens, two individuals started mating. Guard bees continually monitored the two beetles, sometimes flying in close and almost buzzing the beetles, at other times flying into the beetles. On one occasion the male tried to kick out at the guard bee. Otherwise the beetles did not seem to be disturbed by the presence of the guard bees. The mating process was a long affair of 45min and we captured on video a foot-tapping display by the female.

A mating pair of T. decemguttatum. The larger female is eating a honeybee during the mating act.

Video: Mating beetles with female eating a honeybee

After mating was complete, 4 – 6 beetles were spotted in the vicinity of the nest, emerging from different directions. The activity at the nest was heightened, while the sound from the bees changed and became louder. Guard bees started zig-zagging close to the ground through the undergrowth and between the plants and restiads and patrols became more prolific. The beetles started hunting, running up the sandy clearing directly under the flight path of the foragers, sometimes in pairs, and sometimes at least three were close to the nest. One of the beetles ran up the rock face, along and down, only to drop into the nest entrance from the rock overhang above. Another beetle ran up a cluster of a grass-like plant and waited for an opportunity to hunt. Several returning and emerging bees became caught in the curly restiads protruding into the nest entrance. In addition, the bees of this colony were unusually clumsy, often landing upside down or falling sideways, a phenomena only otherwise seen at one other nest. In fact, this nest is the closest in proximity to the nest we had aptly named “Clumsy Nest” after this extraordinary behavioural trait. We considered whether these nests were directly related.

These beetles are formidable hunters and fast on foot. They quickly caught and subdued any forager (female worker bee) or drone (male bee) tangled in the restiads. The guard bees immediately chased the beetle predator, probably in response to the distress pheromone discharged by the trapped bee, but the guard bees had little impact on the beetles and their hunting activities. The beetles with their mouthparts adapted for biting and chewing (Skaife 1979) were quickly able to consume the bees under cover of the fynbos. After one beetle carried away a drone in its mandibles, another beetle came towards it, but there was no tussle and the oncoming beetle merely turned away. The beetles appear not to share their prey. On several other occasions we witnessed fighting amongst the beetles with attacks from behind and two males rolling as if in a skirmish.

Video: Ten spotted ground beetle using a scissor-like action of its mandibles to eat a honeybee

It did not appear as if the beetles known locally as “Oogpister” used their chemical defence mechanism to squirt formic acid in response to feeling threatened (Scholtz & Holm 1985) by the bees. The local name is derived from the squirting of this foul and irritating liquid into the eyes or mouth of predators such as lizards, toads, birds and various mammals. The chlorine or bleach-like odour is easily perceptible if the beetle feels threatened, causing it to squirt this liquid consisting of Benzoquinine compounds. The aposomatic or warning colouration of red and black is usually a deterrent to such predators.

ten-spotted beetle and southern rock agama eating bees

The heightened bee activity between 12:30 and 13:30 attracted not only the Ten-spotted beetles, but also Black girdled lizards and Southern rock agamas. Two smaller orientation flights took place during this period amidst loud buzzing sounds from the honeybee colony. There were a number of drones present. The beetles often took cover in a protected nook slightly inside the nest recovery area and close to where many of the bees clumsily landed. Particularly the drones would land, walk up and along the back wall and then down and through the nest entrance hole in the propolis wall.

Rock agama eating honeybees with scatterings of drones

Black girdled lizard after predating on a honeybee

Since documenting this behaviour at ‘Nest 93’, we have since seen it at other nests. By additionally preying on dead bees that have been removed from a nest, these beetles play a vital role in the wider hygiene of the nesting site. When a beetle thought itself overly formidable at ‘Hope Nest’ and ran in under the ball of bees hanging from their comb, a number of guard bees quickly engulfed it and grounded it indefinitely.

Ten spotted beetle upside down in the leaf litter below the colony and grounded indefinitely

The presence of this carabid beetle species is just one example of adaptation to the largely ground-nesting behaviour of the Cape honeybee in the fynbos biome. It highlights the importance of protecting natural habitats to foster species biodiversity; a biological diversity alive with a variety of living organisms and natural processes.

Male T. decemguttatum with evaginated internal sac of the aedaegus.

It is thought that the behaviour of the male ‘blowing bubbles’ with the internal sac spreads sexual pheromones to attract females for mating.

With many thanks to Dr Manfred Uhlig, Museum für Naturkunde Berlin, for his invaluable input.

The authors at work:

References

Kuhlmann, M. (2010). More than just honey.

Scholtz, C.H. & Holm, E. (1985). Insects of Southern Africa. Butterworths, Durban. 502 pgs.

Skaife, S.H. (1979). African Insect Life. Struik. 279 pgs.