Nesting in dense groups attracts parasites and predators, yet these aggregations persist. The very feature that seems risky creates the system’s complexity.
Karin Sternberg
For wild bees, a dry riverbed serves as a natural corridor through otherwise open terrain. Its meandering course offers landmarks to navigate by, riverbanks that shelter from the wind, scattered patches of flowers, and soils with just the right texture for burrowing.
Tiny Bembix at its nest site on the dry riverbed.
These conditions make it an ideal nesting habitat for species that favour sandy, well-drained ground. In the Karoo, such conditions are common along ephemeral rivers where sand wasps like Bembix dig into the sediment, and for ground-nesting bees, which constitute the majority of solitary bee species globally.
A riverbank is more than a physical feature; it’s a living record of time. Its layers mark past floods and long droughts, changes in vegetation, even ancient climates. In South West Angola, I recently stood before cliffs that revealed stories from a different era, telling of vanished seas, holding fossils of mosasaurs and plesiosaurs in their bone-beds. Here in the Karoo, there are riverbank stories that are still very much alive, written in sand and clay, and unfolding in the form of bees and their intricate communities.
At first glance, a sandy riverbank here looks unremarkable as a sheer wall of compacted earth, a few tufts of grass, roots, the odd shrub, and a scattering of stones. But come closer on a warm spring morning and the surface moves to a low, vibrating hum. Holes dot the bank like pinpricks, and from each one, bees emerge, darting into the air before disappearing again. What seems like just an eroded sandbank is, in fact, a thriving bee aggregation.
Nesting in such dense groups might seem, from an evolutionary standpoint, a bad idea. Parasites and predators quickly notice abundance. Yet these aggregations persist. The very feature that seems risky is what makes the system thrive.
A Spring Awakening
Anthophora wartmanni bees nesting in the river bank
By early September, activity on one such bank at Wolwekraal Nature Reserve is at its peak, continuing through October. It hosts a dense aggregation dominated by Anthophora wartmanni Friese — shaggy, flower-loving digger bees, large-bodied and fast-flying.
The females work tirelessly, provisioning their larvae with pollen and nectar, navigating back to the correct burrow guided by scent. Occasionally one makes a mistake, entering the wrong tunnel before backing out almost immediately, suggesting that each nest carries its own unique chemical signature.
The Anthophora may be the most conspicuous residents, but they are not alone. The same bank also supports populations of Megachile (leafcutter bees), Amegilla, Plesianthidium, and Afroanthidium species, each with slightly different nesting needs and seasonal timing.
Top row (left to right): Anthophora, Megachile, Pachyanthidium. Bottom: Anthophora wartmanni.
Inside the bank lies a maze. Many burrows branch into two or more tunnels, a network that offers opportunity and danger in equal measure. Parasitic wasps such as the metallic cuckoo wasps (Chrysididae) and the velvet-armoured mutillids use their smaller size to slip between tunnels, entering one hole and emerging from another. The larger bees are confined to their own passages, always using the same entrance.
Nest entrance holes in the riverbank, some with several passages branching from the main tunnel.
Anthophora male warming up.
Male bees of several species patrol the bank, flying back and forth in search of emerging females. It’s an efficient mate-location strategy and for some species seems better than waiting around at flowers, though it does mean that predators quickly learn where to find them.
The Parasites and Their Strategies
Dense nesting aggregations attract a diverse gathering of parasites and kleptoparasites, each exploiting the concentrated resource of provisioned brood cells.
Velvet Ants
Wingless female mutillid wasp, also shown here dusted with pollen after visiting a bee nest cell.
Among the most conspicuous visitors are the so-called “velvet ants” — female mutillid wasps, wingless, densely hairy, and quick-moving. They scurry over the sand in the midday heat, pausing briefly to inspect a burrow entrance before moving on. Their mission is simple but effective: find a bee’s nest, slip inside, lay an egg on the host’s larva, and leave. The developing mutillid eats the larva and its food supply. Adults, oddly enough, feed only on nectar, a dramatic dietary shift from meat to sugar that would confound most nutritionists.
A female mutillid wasp moves swiftly between the bee tunnels
Male mutillids, in contrast, keep their wings and were often seen inspecting nest entrances, probably in search of emerging females rather than hosts. This strong difference between the sexes, with winged males and wingless females, reflects how each has evolved for a different purpose: males to locate mates and females to locate hosts.
Winged males look into nest entrances, searching for emerging females
Cuckoo Wasps
Then there are the chrysidid wasps, shimmering metallic-green under the Karoo sun. The flashiest of these wasps glitter in brilliant hues of emerald, turquoise and copper. Their colours are structural — microscopic prisms in the cuticle refract light so that even a dead specimen never fades (C. Eardley, pers. comm., 30 September 2025). They slip in and out of bee tunnels, sometimes reappearing some distance away. One pair was seen mating near the bank, suggesting that for the parasites, this place serves as both hunting ground and courtship arena.
Several species of metallic-green cuckoo wasps (Chrysididae).
Cuckoo Bees
A Coelioxys bee — a cleptoparasite that lays her eggs in the nests of other leafcutter bees.A Thyreus bee — the strikingly patterned “cuckoo bee” that lays her eggs in the nests of Amegilla species.
Cuckoo bees, including Thyreus and Coelioxys, are also regular visitors. They specialise in parasitising species like Anthophora and Amegilla. Their method differs slightly from that of the wasps: they lay their eggs in completed brood cells, leaving their larvae to consume the pollen store rather than the host larva itself. Either way, the intended offspring loses, with the host larva eventually starving.
Flies
A parasitic bee fly (Bombyliidae) investigates a nest entrance, collecting sand to coat its eggs before flicking them into bee burrows.
Flies join in with characteristic ingenuity. Bee flies (Bombyliidae) hover near entrances, flicking sand-coated eggs toward burrows. The sand adds weight, propelling the eggs deeper and preventing them from drying out. Once inside, the tiny larva seeks out the host’s brood and parasitises it.
Tachinid flies such as Rondanioestrus apivorus take a more direct approach: their eggs hatch almost instantly, and the larvae burrow into returning bees, developing inside their hosts. Efficiency comes in many forms.
Left: A tachinid fly (Rondanioestrus apivorus) lies in wait on the river bank, watching for returning foragers and, right, flying close to a nest entrance.
Predators and Opportunists
Ants
Ants are part of the story too. Their nests lie directly beneath the bee aggregation, and they emerge late afternoon as temperatures moderate and bee activity declines. Small ant species such as Anoplolepis steingroeveri and the larger, square-headed Tetramorium were observed carrying bee larvae from Anthophora tunnels, possibly scavenging or predating on brood cells damaged during excavation or parasitism. They were remarkably adept at transporting larvae down the steep vertical walls to their nests below. Sometimes their activity caused partial blockages in the bee tunnels, leaving some Anthophora females hovering at the entrances or trapped inside.
Among them, the Balbyter ant was also recorded. Ants likely play a dual role: as opportunistic predators on vulnerable brood and refuse removers, carrying off dead larvae and decaying provisions, like pollen. Their late-afternoon peak in activity minimises direct confrontation with actively provisioning bees.
A Balbyter ant (Camponotus fulvopilosus) pauses at the entrance of a bee burrow — part scavenger, part predator, and always alert to opportunity.An ant drags away a pollen ball, recycling what’s left behind
Other Hunters
A solifuge, one of the lightning-fast, spider-like sun spiders was spotted nearby. These arachnids can subdue adult bees, though they more often hunt smaller prey. Karoo scrub-robins (Cercotrichas coryphaeus) were also seen foraging along the bank, gleaning ants from the ground, bees from flowers nearby, and scanning the vertical surface for movement. It’s a reminder that vertebrates, too, are part of the system.
Shifts Through the Day
Activity at the aggregation follows the sun. At midday, when the sand is too hot for ants, bees are most active. As the sun lowers, bees retreat, ants emerge, and birds intensify their foraging. This daily rhythm allows many species to share the same narrow strip of habitat without direct competition.
Early in the morning, female bees rest on the sand, absorbing warmth before flying off. It makes them visible to predators, but in the cool Karoo mornings, it’s essential for warming their flight muscles.
A Living System
The more time I spent at this riverbank, the more its complexity unfolded. It’s a place where a diversity of species interact in patterns shaped by millions of years of coevolution. Bees emerge from countless burrows. Parasitic wasps patrol the surface. Flies hover at entrances. Ants appear and become abundant in the late afternoon. Birds scan the sides of the riverbank for movement. The aggregation exists because every element aligns perfectly: the substrate is right, the bank catches the early morning sun, and the site lies within reach of flowers. Change one variable and the system falters. That fragility is what makes biodiversity conservation so complex, and so essential. It’s not enough to save species in isolation; we must protect the very places that make their coexistence possible.
Dry riverbeds and eroded banks like this one are far more than geological features in the Karoo. They are irreplaceable threads in a vast ecological fabric. Edges where life concentrates, adapts, and thrives. In protecting these fragile corridors, we protect the processes that create diversity itself.
Aggregations as Ecological Hubs
Why do bees nest in dense groups when it attracts so many enemies?
When solitary bees nest in dense groups, they face greater risks: parasites, kleptoparasites (like Thyreus), predators, and even competition for space. From the outside, it seems counterintuitive. Why not nest alone, far from danger?
But these dense aggregations also bring key advantages, which is why they persist:
Safety in numbers: Predators and parasites become diluted across hundreds of nests. Each individual bee’s chance of being targeted decreases.
Environmental advantages: The bees tend to choose the best microhabitats — in this case, the warm, stable riverbank soils that make nesting and brood development more successful.
Social cues: Bees can locate suitable sites by following others or detecting the scent of past nesting activity, saving energy and risk in finding a new site.
Mating opportunities: Males and females find each other more easily around aggregations.
Evolutionary innovation: The close proximity of many species and individuals fosters complex ecological relationships, from parasitism to species learning how to coexist, that drive adaptation and diversity.
So, what seems risky (high predation and parasitism) is also what creates ecological richness and resilience. The “greatest risk” (clustering together) becomes the “greatest strength” (a dynamic, evolving system that sustains itself through diversity). Aggregations like this function as natural laboratories for studying coevolution, host-parasite dynamics, and community assembly. But they’re also conservation priorities. These systems depend on dynamic landscapes like seasonal flooding, bank erosion, substrate renewal. Stabilising riverbeds or preventing natural erosion eliminates the very processes that create nesting habitat. Understanding solitary bee ecology is urgent as they’re critical pollinators globally, yet far less recognised and studied than honeybees or social species. This dry riverbank, so easily overlooked, teaches us that biodiversity isn’t just about individual species. Rather, it’s about the landscapes that bring communities together and the processes that maintain them.
A female Megachile taraxia exiting the mud nest she is constructing on Wolwekraal.
It was spring on Wolwekraal Nature Reserve in the arid Karoo, and the bare patches of ground were alive with solitary bee activity. Besides the busy work of Tetraloniella brevikeraia—the short-horned long-horned bees—other solitary bees were active, too.
The :deflation hollow, its surface cemented by fine dust particles, was bordered by scattered stones and sparse vegetation. Several of the larger stones provided ideal nesting sites for another solitary bee, Megachile taraxia. Unlike the better-known mason bees (Osmia), which usually build in cavities, this species constructs exposed domes of mud on rock surfaces, hence its description as a mud-nesting or “dauber” bee. Until recently, M. taraxia was known only from the male and recorded at just two localities, one in Namaqualand and the other in Gauteng. Finding it here, and finding both males and females, seemed an unusual and important turn up for the books.
Stones on the edge of a deflation hollow at Wolwekraal, providing firm foundations for Megachile taraxia mud nests.
I first noticed a female sitting on a prominent stone. At a glance I thought she was resting; she had been circling me for a while with a deep buzz. Only when she alighted did I see a small wet patch. On closer inspection, I realised I was looking at a mud nest. Without that faint spot of moisture, it might have seemed no more than a chance splash of mud.
Female Megachile taraxia completing the outer seal of her mud nest using saliva.
Reading through the literature on how such mud nests are built, I came upon the works of Jean-Henri Fabre (1913) in his celebrated Souvenirs Entomologiques. He applied the name “mason bees” to those that build their cells with materials similar to our own building supplies. “It is masonry,” he wrote, “but made by a rustic workman, better used to dried clay than to hewn stone.” In his essays he describes the mud-dome nests of Chalicodoma bees. While Megachile taraxia belongs to the subgenus Pseudomegachile, Fabre’s evocative accounts of Chalicodoma nest building, with its mixing of clay, sand, and saliva into a stone-hard mortar, help to illuminate how enduring these dauber bees’ constructions can be. He writes that a calcareous clay is mixed with a little sand and kneaded with the mason’s own saliva (a mix of long-chain hydrocarbons, mainly hentriacontene and tritriacontene, produced by the labial glands). Damp spots that might make the work easier and spare her saliva, are disdained by this dauber bee, which refuses fresh earth for building, just as our builders refuse old plaster and lime. Such materials, when soaked with humidity, would not hold properly. What is needed is a dry powder that readily absorbs the disgorged saliva and, with its albuminous principles, forms a kind of Roman cement that hardens quickly, something like what we obtain with quicklime and egg white. The glandular mixture is used not only as mortar but also spread over the exterior of the nest to render it hydrophobic. The mud dome dries as rapidly as our hydraulic cements, becoming almost as hard as stone. A strong knife blade is needed to cut it. In its final form the nest scarcely recalls the original work, yet it lasts through the year without notable injury. The dome remains much as it was at the start, so solid is the masonry; only the round holes, corresponding to chambers inhabited by the larvae of the past generation, mark its surface. Such dwellings, needing only minor repairs, save much time and effort. Mason bees reuse them, and build new nests only when old ones fail.
Various stones on Wolwekraal showing Megachile taraxia mud nests, their circular openings indicating completed development and emergence. The original mud nest where the first M. taraxia female was discovered is shown top left.
Ten months after my first sighting of the female M. taraxia on her mud nest, and with the early onset of warm spring weather, the first holes appeared in the mud dome nests on Wolwekraal, marking the emergence of the next generation. Within weeks, one hole became four, and soon I began noticing many more nests I had previously overlooked, camouflaged until the perfect round openings revealed them.
Megachile taraxia males and females both utilise mud nests for resting. Top: Female resting in a nest cell (left) with close-up view (right). Bottom: Male resting in mud nest (left) with close-up detail (right).
In one abandoned hole I found a male asleep. On other occasions, I discovered females sleeping inside nests they were still constructing and provisioning. I spent several hours a day watching a female at work. She arrived with her crop full of nectar and her scopa bright yellow with pollen. Head first, she entered the mud cell to disgorge nectar. Once emptied, she backed out, turned, then reversed in to deposit pollen, brushing it from her abdomen with her hind legs. She made several trips to build up a paste-like mass of nectar and pollen, shaping it into a ball like playdough. When the provisioning was complete, she laid an egg and sealed the cell. Only then did she begin work on the next, each cell fully finished before starting another. The rock beneath her nest proved a firm and lasting foundation.
Megachile taraxia female provisioning behaviour sequence. The female arrives with her crop full of nectar and scopa laden with bright yellow pollen, enters the mud cell head-first to regurgitate nectar, then backs out, turns around, and reverses into the cell to deposit pollen.
At another location within Wolwekraal, I discovered more mud nest sites and watched both male and female M. taraxia visiting Blepharis mitrata flowers within a 50-meter radius of these nests. This dense, hard-leaved plant is locally called “scorpion bush” for its formidable spines, or “shooting seed” for its explosive seed pods when wet, and appears to be a preferred foraging resource. The males, who emerge from their mud cells first, use a smart strategy: they wait at the flowers where females come to collect pollen, which is the essential protein food for their developing larvae.
Female arriving at Blepharis mitrata to gather nectar and pollen.
By positioning themselves on or near the flowers, males dramatically improve their chances of meeting a potential mate. Between flower visits, I watched males sunbathing on rocks, stones, and patches of bare sand to warm up, often returning to the same favourite spots. Following these males actually helped me locate more nest sites, as they regularly checked mud nests, apparently monitoring for newly emerging females.
Megachile taraxia foraging and mate-seeking behavior. Left: Female with head deep in Blepharis mitrata flower collecting nectar and pollen. Right: Male basking for thermal energy while waiting for females.
Mating typically occurs either at flowers or near nest sites. Male solitary bees have developed remarkable features for finding females, including modified eyes, antennae, and legs that work like sophisticated detection equipment. Some species have even evolved enlarged brain regions that boost their vision or sense of smell, depending on whether they track down their partners by sight or scent.
Watching these bees at work left me with a sense of awe for their resilience and ingenuity. In the middle of the Karoo, on bare stones near a wind-swept deflation hollow and exposed to temperature extremes, a species so seldom recorded constructed homes almost as enduring as the stone they were built on and carried on its quiet cycle of life. To stumble upon Megachile taraxia here, in numbers and with nests so well hidden, felt like uncovering a treasure. It’s one that reminds us how much there is still to discover, and how much depends on noticing the small, stone-hard wonders at our feet.
Male Megachile taraxia emerging from a mud cell after resting overnight.
A glimpse inside the mud nest: the brood cells are lined with glandular secretions, though little is known about this aspect of bee nesting.
Field Notes from Wolwekraal:
While documenting the story of Megachile taraxia, I often found myself lying so still and so quietly that it felt as though I had become invisible to the creatures around me, or perhaps absorbed into the very terroir of the place. On several occasions, giant tortoises walked past within only a few metres, undisturbed by my presence. Once, a grey mongoose passed less than a metre away, its nearness betrayed only by the scattering of small stones shifting beneath its paws. These encounters made me feel part of the ecology of Wolwekraal, allowing me to observe not only the focal species but also other elements of the ecosystem.
A giant leopard tortoise on Wolwekraal Nature Reserve, Stigmochelys pardalis pardalis.
References:
Buchmann, S. (2023). What a Bee Knows: Exploring the Thoughts, Memories, and Personalities of Bees. Island Press.
Danforth, B. N., Hinckley, R. L., & Neff, J. L. (2019). The Solitary Bees: Biology, Evolution, Conservation. Princeton University Press.
Fabre, J. -H. (1913). Insect Life: Souvenirs of a Naturalist. MacMillan and Co., Ltd.
Some Xylocopa have interesting adaptations, like Xylocopa io with its elongated middle legs.
A male Xylocopa io with a distinctively long middle leg, visible on the right of the bee.
Xylocopa bees are mostly large, robust bees. They are solitary bees, unlike honeybees that live in colonies. There are many species of carpenter bees and they are important pollinators. They 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 nectar and pollen mixed together, on which a single egg is laid.
Recently while out hiking we spotted a male Xylocopaio high on a ridge between Prince Albert and the Swartberg Mountains in the Karoo. Not much is known about this species, and even less is known about the female X. io., but one interesting feature of the male is his two long middle legs.
A male Xylocopa io hovering, revealing its unique extra-long middle leg.
Insects are generally bilaterally symmetrical, so this male—with only one long middle leg—may have had a narrow escape from a bird, or something similar.
To attract females, Xylocopa males generally hover around a flowering shrub, then dart off, only to return seconds later to hover briefly again.
Males patrol a patch of flowers, which females visit while foraging, in order to mate with them. A patrolling male will aggressively chase away other males that intrude on his territory. The success of these encounters is enhanced by the permeation of a sex pheromone released by the male while patrolling his patch of flowers.
Male Xylocopa caffra on Aspalathus capensis (Cape capegorse).
Male X. caffra with less exposed membranesMale exposing two interstitial membranes as he releases a sex pheromone
Xylocopa caffra males make quick circuits over an area of several square meters. What is most fascinating is that the normally completely yellow male, when hovering around its patch of flowers, lowers its abdomen and exposes two of its interstitial membranes which appear as two black bands on the abdomen. This behavior is most likely a way for the male to release a sex pheromone, serving both as a species-specific chemical signal and as an attractant for females. When the male momentarily darts away, the membranes are less exposed compared to when he hovers.
Males of the carpenter bee Xylocopa hirsutissima have a different strategy: they fly to the top of the mountain where they spread mandibular gland secretions over the ventral surface of their abdomen while hovering in the air awaiting the female.
A rare sight: a male Xylocopa io with a strikingly long middle leg, a unique trait of this elusive carpenter bee.
In Xylocopaio, the male’s elongated middle legs are believed to be an adaptation for mating. During mating, the male launches into the air after the female, using his extended legs to grasp her along ridges below her three small simple eyes, known as ocelli. Interestingly, another species, Xylocopa flavrufa, exhibits a similar mating behaviour: the males also pursue females in flight, using their long middle legs for mating.
The parasitic fly, Hyperichia bifasciata, thought to mimic the carpenter bee Xylocopa caffra, .
Found in the same area as X. io, was a species of fly, Hyperichia bifasciata, known to mimic specifically Xylocopa caffra. The fly’s name, bifasciata, suggests that it may have two prominent markings or bands (the “bi-” prefix means “two” and “fasciata” refers to bands or stripes). There exists much individual variation in the colours of the bands on the thorax and abdomen, from whites to yellows. Hyperechia flies are notable for their parasitic relationship with carpenter bees. The larvae are predacious on those of Xylocopa. As adults, these flies feed on bees and wasps. H. bifasciata is not too picky and so will parasitize other Xylocopa species as well.
References:
Grünberg, K. 1907. Zur Kenntnis der Asiliden-Gattung Hyperechia Schin. (Dipt.). Deutsche Entomologische Zeitschrift: 515-524
Van Bruggen, A.C. A preliminary note on the genus Hyperechia
Velthuis, H.H.W. and Camargo, J.M.F. de 1975. Further observations on the function of male territories in the carpenter bee Xylocopa (Neoxylocopa) hirsutissima Maidl (Anthophoridae, Hymenoptera. Netherlands Journal of Zoology 25(4): 516-528.
Watmough, R.H. 1974. Biology and behaviour of carpenter bees in southern Africa. The Journal of the Entomological Society of Southern Africa. 37(2): 261-281.
Occasionally, biodiversity might just be thriving beneath our feet.
Karin Sternberg
The deflation hollow which is home to so much diversity
The resilient Karoo landscape
During my explorations of the Wolwekraal Nature Reserve, in the arid Karoo region of South Africa, a seemingly desolate stretch of land consistently caught my attention. This area, characterised by hard, ancient sediment, served as a shortcut from the jeep tracks to a wild colony of honeybees nesting in an aardvark (antbear) burrow. The flora surrounding this bare ground is a stark reminder of the Karoo’s remarkable resilience, showcasing a rich tapestry of species that thrive in one of the world’s extreme climates. Over centuries, the vegetation here has adapted to withstand dramatic temperature fluctuations, from severe winter frosts to scorching summer heat at times exceeding 50°C, often enduring prolonged periods of drought.
Yet, amid this tenacity, certain areas of the landscape remain barren and hardened. Recently, I buried a wild hare—a tragic victim of roadkill—in an aardvark dugout; a deep, empty cavity, in an area of hard ground I could never have dug myself. My sister, with her characteristic humour, had remarked, “Everyone needs an aardvark.” As I reflected on the hare’s untimely death, I was once again captivated by the number of solitary bees nesting in holes on the inner edges of these burrows. Like the wild honeybees in these landscapes, many species are dependent on the :aardvark for their nest sites; a reminder of nature’s interconnectedness. All around the dugout vibrant yellow swathes of Gazania lichtensteinii were in flower, their annual beauty enhanced by early winter rains.
Top row left to right, solitary bees living on the edge of this aardvark dugout: Samba female, Colletes female, and a Patellapis female.
Misconceptions of bare ground
The seemingly lifeless stretch of ground, a wind-scoured deflation hollow, was located close to this dugout. Deflation hollows form where vegetation is lost allowing wind to remove sandy topsoil and expose a hard subsoil comprising desert dust cemented with calcium carbonate. They are often associated with stone age human settlements of hunter-gatherers and herders. At this particular deflation hollow, there are various stone tools made from chert including a stone arrowhead. Standing on this hardened ground I was struck by a common misconception: that bare earth signifies death. Often dismissed in environmental assessments, this apparently barren, hard ground was, in fact, teeming with life and intrigue. Initially mistaking the sounds I was hearing for a drone congregation area – where honeybee males dart through the sky waiting for a queen – I quickly realised that the sound was emanating from the ground. A closer look revealed a fascinating gathering of male Tetraloniella cf. brevikeraia bees. These short-horned longhorn solitary bees were eagerly vying for a chance to mate with a female as she emerged from her underground nest. Although solitary by nature—females work alone in building nests and provisioning food—these bees form dense aggregations in favourable environments. The apparent barrenness of the ground belied its role as a prime breeding ground, and I counted an astonishing 114 nests in the vicinity.
The author documenting the diversity on the deflation hollow; it is so unassumingly rich in life (photo: Collette Hurt)
The evolutionary journey of bees
The evolutionary journey of bees, stretching back around 100 million years, began with solitary, predatory mud-dauber wasps, coinciding with the rise of flowering plants. Today, bees exhibit remarkable diversity, particularly in arid regions such as the Karoo where solitary species thrive. They range in size from a mere 2mm to 39mm and come in various forms, from densely hairy to smooth and shiny, often adorned with striking colours, masks, stripes and patterns. Most species of solitary bees prefer to nest in the ground, often using plant materials or resin to line their nests. On this hard bare ground, the thriving community of Tetraloniella served as a vivid testament to the vibrant life hidden beneath the surface.
Dynamics on the deflation hollow
The deflation hollow measured 24 m by 13 m, with nests concentrated in a mere twelve square meters. The spacing of the nests varied, with some holes nearly touching while others were separated by more than 20 cm. The solitary male bees, have one primary role: to mate. Males are remarkably specialised, with their entire existence revolving around this singular task. To prepare for mating in the earlier hours of the day with temperatures in the lower teens, the males press their bodies against the sun-warmed sand. In September, when daytime temperatures can reach 28°C, the ground can heat up to a hot 44°C. Males dart close to the surface in circular and zigzag patterns, seeking the radiated warmth that boosts their speed. I counted 26 males on this day, but their numbers waned with each subsequent day. I could only imagine how busy this aggregation had been at the beginning of mating season. Many of the males were covered in bright yellow gazania pollen from hasty sips of nectar essential for their energy needs.
A small section of the Tetraloniella nest aggregation
Top row: Shortly after 9 a.m., the first male Tetraloniella bees make their appearance on the deflation hollow, braving air temperatures below 15°C. Seeking warmth, they press their bodies against the sun-soaked sand, where ground temperatures already reach the mid-20s. Middle + bottom row: Males congregating around the nest holes, waiting for the females to emerge
Coexisting species: The diversity of life
In addition to the Tetraloniella bees, there were other bees thriving in this environment. Among them were various species of leafcutter, dauber and mason bees (Megachilidae) that make their nests in pre-existing burrows. Initially chased by the males, they started inspecting holes abandoned after the females emerged. These bees possess unique nesting techniques and have the broadest range of nesting behaviours. Unlike honeybees that collect pollen on their hind legs, the Megachilidae collect pollen on tufts of red hairs on the underside of their abdomen, known as a scopa. When this is fully packed with pollen it is a bright patch of colour.
Leafcutter bees construct thimble-like cells lined with leaves or petals to protect their young from moisture and predators. For their nests they were using both leaves of krimpsiektebos (Lessertia annularis) as well as gazania petals. Both of these plants contain extremely bitter compounds that possibly serve to deter parasites and provide beneficial antimicrobial properties. Another of the females (Hoplitis sp.) used chewed, reddish-pink plant pulp together with a mouth secretion to line her burrow. The source of the plant was not established but was similar in colour to bellbush (Hermannia grandiflora) flowering nearby. Similarly diverse are the materials used for plugging the entrances, with some bees choosing a combination of leaf pieces and mud, while others used mud and stones. The collected pollens for the provision of larvae with food came from plants distinct from those used for nesting materials, possibly from honeybush (Melobium candicans) or the brightfig (Rushia bijliae), both in flower and in range of the nest site and on which the bees were sighted. Each female completed one burrow per day.
Megachilid bees with their diverse nesting techniques, utilising burrows abandoned by Tetraloniella bees
Further careful study of the ground revealed a Camponotus rufopilosis (balbyter) ant carrying a dead conspecific. With mandibles featuring 5 to 7 teeth, these ants defend themselves by spraying formic acid when threatened. Amidst the male Tetraloniella bees, this ant dropped its prey and assumed a defensive stance. Larger, robust dauber bees (Megachile nasicornis) were also sighted, distinguished by their different, deeper sounds, and by their striking, singular patches of black and white coloration. They were also on the lookout for abandoned Tetraloniella nests to use for their own reproduction.
Balbyter ants (Camponotus rufopilosis) and the larger, more robust, dauber bees (Megachile nasicornis) on the deflation hollow
While documenting these interactions, a brown-and-white striped fly (probably in the genus Parisus) scraped her abdomen along the ground and then hovered above several bee nest holes. This Bombyliidae fly is known to parasitise a range of insects including bees. Hovering above a nest, the fly deposited 33 eggs in less than a minute. To lay eggs in this way, some Bombyliidae have a chamber near the ovipositor filled with sand which they stick to the egg, giving it enough weight to shoot deeper into the host nest and helping to prevent the egg from drying out too much. This observation might represent a new host record, and underscores the intricate relationships between host and parasite.
Top row left to right: A Bombyliid fly filling her ovipositor with sand granules, then hovering over a nest burrow to lay eggs. Bottom row left to right: A male Tetraloniella bee investigating the fly; the fly shooting an egg into the burrow (spot the egg!)
A climax
The climax of my observations came when a chaotic scrum formed around a single nest hole, where male bees gathered in a frenzied attempt to mate with the emerging virgin female. In this state where the males were fixated on the hole and seemed vulnerable to predation, I wondered if the female released a pheromone to signal her arrival. As mating commenced, the male produced a sound known as “piping,” a result of the vibrations created by the wing muscles. The male, mounted on the female, used his antennae to possibly release a volatile pheromone, engaging in a behaviour known as antennal fanning. He fans his antennae near hers without direct contact. Research indicates that a courtship pheromone may exist in bees, which is believed to induce receptiveness in the female. Clasped tightly to her, other males attempted to dislodge him, displaying a complex mating struggle. Uniquely, the female grasped a red stone during copulation, remaining mostly still amidst the chaos around her. After more than 3 minutes of mating the primary male was dislodged, and the female executed an intense spinning motion to escape, eventually flying off to establish a new nest elsewhere. (To watch the incredible mating video, click here.)
Top: A scrum of males around the hole where the female is about to emerge. Top right and middle: a tussle ensues as one male battles another for the opportunity to mate with the female. Bottom: the mating pair.
I was unable to establish the mode of excavation of the nests, or whether this species use pre-existing nest cavities as the Megachilidae do, though did note that no turrets or soil mounds were present. Similarly, I could not locate the males at night, though these are thought to form sleeping clusters hanging from a branch.
A rich tapestry of creatures
While at the study site, I encountered numerous other creatures. Among them were a rock agama, Namaqua sand lizards, cryptic Sphingonotis grasshoppers, beetles, robber flies (Asilidae), and a wingless female mutillid wasp (velvet ant). This ant-mimicking wasp was intriguing as she used her abdomen to push aside stones to enter the nest of a solitary bee—they are parasites of the larvae of ground-nesting bees. I also heard barking geckos and, with much patience, managed to photograph one in its burrow. Overhead many kinds of birds flew by, including two pale chanting goshawks. Beyond this deflation hollow, I discovered an extraordinary mud nest in the shallow of a stone; a Chalicodoma mason bee builds her nest in a hollow on a rock, sealed over by sand cemented with a secretion from her mouth.
The hidden life beneath our feet
This study illuminated a critical lesson: even the most unassuming, barren stretches of land may be far from lifeless. They may harbour intricate ecosystems, teeming with life that defies initial perceptions. The conservation of these natural nesting habitats is crucial for the survival of solitary bees and other species. Therefore, these often-overlooked spaces must be included in environmental impact assessments (EIAs). Bare ground is too rich in life to be dismissed; recognising such ecosystems is essential for maintaining biodiversity and ecological resilience, while still allowing for erosion control and restoration efforts such as reseeding rehabilitation and replanting on damaged lands or vacant erven as a means to enhance ecosystem health. Remember, biodiversity might be thriving unseen beneath our feet.
From top to bottom: Wingless female mutillid wasp (in contrast, the males can fly) entering a nest burrow of a solitary bee; Sphingonotis grasshopper and a frantic surface beetle; leafcutter bee and a pale chanting goshawk; Chalicodoma bee and a barking gecko
ACKNOWLEDGEMENTS:
Dr Sue Milton-Dean of Wolwekraal Nature Reserve
Dr Connal Eardley and Dr Michael Kuhlmann for their help with bee identifications
Dr John Mark Midgely for his assistance with fly identification and behaviour
Prof Ben-Erik van Wyk for his ID of Lessertia annularis and his extensive knowledge of plant compounds
Dr Geoff Tribe and Collette Hurt for their assistance with other species and stone artefacts
REFERENCES:
Batra, S.W.T (1984) Solitary Bees, Scientific American Vol. 250, No. 2, pp. 120-127. Scientific American, a division of Nature America, Inc., 8 pgs
Fuchs, M., Kandel, A.W., Conard, N.J., Walker, S.J. and Felix-Henningsen, P. (2008).
Geoarchaeological and Chronostratigraphical Investigations of Open-Air Sites in the Geelbek Dunes, South Africa. Geoarchaeology.
Gess, S.K. and Gess, F.W. (2014). Wasps and bees in southern Africa, SANBI Biodiversity Series 24.
Michener, C.D. (2007). The Bees of the World, The Johns Hopkins University Press.
Packer, L. (2023). Bees of the World. A Guide to Every Family, Princeton University Press.
Romani, R., Isidoro, N., Riolo, P., and Bin, F. (2003). Antennal glands in male bees: structures for sexual communication by pheromones? Apidologie 34 (2003) 603-610.
Skaife, S.H. (1963). Strange Adventures among the insects, National Boekhandel.
Slingsby, P. (2017). Ants of Southern Africa. The ant book for all, Slingsby Maps.
An Environmental Impact Assessment (EIA) is nowadays required before any development can proceed – yet how accurate are they? The year in question, the season, the size and duration of the survey (weeks/months/years) can influence the outcome of the EIA. What would constitute a minimum duration for such a survey? An ecological research project would require a minimum of 3 years, where 5 years is passable, but 10 years would give far better insight. EIAs are often inadequate in terms of genuine environmental protection, and many species are missed, particularly the geophytes and ephemerals, the invertebrates, frogs, birds and bats. Some EIAs are designed to facilitate and even legitimize development where it should not happen. They are mere snapshots in time and miss the far greater, fundamental ecological processes and responses. An erroneous decision could have far-reaching consequences for very sensitive and less well researched areas. The flora and fauna must be researched well, especially in areas that had not previously been well documented.
With sedentary plants and perennials which can be more readily located, identified and enumerated, a reliable assessment is more easily accomplished. Yet seeds from some plants can stay dormant for decades until favourable conditions cause them to germinate. This applies also to the erratic flowering of underground bulbous plants triggered usually by substantial rains. An example of this in relation to the account below is the dubbeltjiedoring, Tribulus terrestris, which prior to the flood was rare on the farm. Following the exceptional rains the unwelcome thorns appeared en masseespecially around the disused sheep pen and along the banks of the once dry streams, forming dense mats with single plants often covering an expanse of one metre or more in diameter and leaving literally thousands of the thorns to germinate when conditions are again favourable.
When it comes to mobile organisms such as birds, animals and insects which can migrate from regions when adverse conditions persist, re-colonization is necessary when conditions improve. This would necessitate ‘refuges’ for such organisms where, within the vast area affected, there are atypical areas that remain favourable due perhaps to underground water or seepages. Would such ‘refuges’ be identified during EIA? Re-colonization can be accomplished by migration or in the case of plants by seeds being blown or carried by animals back into the affected area. This would only be possible if the EIA properly takes into account the region and mitigation of damage and risk is done by judicious sparing of some zones for development.
The cyclical effect on nature through seasonal and climatic fluctuations determines and requires adaptive responses by different organisms. Yet it is surprising to see how readily reactions can occur in response to changes in the status quo. An example of this was the changes that occurred on a farm in the Tanqua Karoo about 35 km north-east of the town of Touwsrivier. Some interesting observations on this farm will be described after an account of recent climatic conditions.
Tanqua Karoo
Fig. 1. The succulent Karoo scrub on the farm with the shearing shed in the far distance.
The karroid vegetation of the Tanqua Karoo is composed of xerophytic, semi-desert shrubland with a large number of succulent-leaved species [Fig 1]. There is no surface water on the farm. A wind-pump supplies ground-water when required. From 20 years ago, average rainfalls were recorded on this farm. Although one year was never the same as the year before, the fluctuations in the fauna and flora were not drastic. However, a drought persisted for the preceding eight years during which time a marked deterioration of the veld was observed. Many succulent plants died and others failed to flower. Many insect species either disappeared or became rare. Four colonies of Cape honeybees (Apismellifera capensis) two of which nested in aardvark burrows [Fig. 2] and two in clefts in shale outcrops [Fig.3], absconded. The annual rainfall over the past decade averaged 102mm with a range of 34 to 226mm. With the exception of 2018, the preceding 5 years had rainfalls of less than 90mm per year. Generally, the rainfall during November and December was <10% of the annual rainfall but in 2021 it was 26mm (37%). It was completely different in December 2022.
Fig. 2. Honeybee nest in a deserted aardvark burrow which was pestered by banded bee pirates.
Fig. 3. Honeybee nest in a crevice in a shale outcrop on the farm.
The drought was broken by recurrent episodes of significant rainfall from November 2022 to May 2023 which were unprecedented for the last 20 years. The rainfall of 143mm in December resulted in a flood. Indeed, the Tanqua Karoo and adjacent regions experienced widespread floods. Dry river streams turned into raging torrents and the sand was washed down from the hills and deposited onto the plain below, leaving a wide river bed with solid shale bedrock. Over the six months of increasedrainfall, the growth of the vygies in particular was particularly good. Whereas one could easily walk in the empty patches between the vygies, they now coalesced into an aggregation as they increased in growth. Vachellia karroo (‘soetdoring “ or karoodoring’) immediately responds to substantial rainfall . Vachellia karroo flowers develop only on the young growth of that season and so growth, dependent on rainfall, precedes flowering by 4 to 5 weeks. Within a short while these trees flowered twice in succession and became an attraction for all manner of insects including beetles, wasps, flies, caterpillars, butterflies, bugs, aphids, and solitary bees … but no honeybees were seen. Presumably the Cape honeybees that were observed collecting water at various seepages throughout the farm were visiting alternative sources which were more profitable.
Fig. 4. The succulent Tylecodon paniculatus which grows on the surrounding hills.
Due to the floods, the Vachellia karroo and Searsia burchellii trees which were scattered along the rivulets had their roots exposed. The roots had been unable to penetrate the shale bedrock but instead had followed along the banks of the river, some being as long as perhaps 12 metres. In most cases it appeared that the combined mass of the roots of a tree was greater than that part above the soil. Another observation was that many of the larger succulent species such as Tylecodon paniculatus [Fig. 4] and Tylecodon wallichii had rotted and collapsed due to the perpetually rain- soaked soil. Surprisingly, larvae of an unidentified longhorn beetle (Cerambycidae) which are usually found in the solid wood of dead trees were found in the soggy, water-laden stems of a T. paniculatus [Fig.5].
Fig. 5. Longhorn beetle larvae in the stem of a rotting Tylecodon paniculatus.
Amphibians
Although five species of snakes and several lizard species occur on the farm, until this flooding no frogs had ever been seen. Yet over a period of at least six months the newly filled hollows in the impermeable shale of some of the riverbeds by seepages contained many hundreds of tadpoles. Two frog species were identified. The Karoo toad (Bufo gariepensis, also named Vandijkophrynus gariepensis)) [Fig.6] can, under favourable conditions, reproduce in large numbers because as many as 20 000 eggs can be deposited by a single female. These distinctive eggs are united into strings [Fig.7] by copious amounts of jelly-like oviducal secretion. The eggs hatch into small, dark tadpoles which concentrate into tight free-swimming clusters [Fig.8]. The adult Karoo toad may vary considerably in colouration but is cryptic in its prevailing surroundings.
Fig. 6. The Karoo toad, Bufo gariepensis.
Fig. 7. A string of Bufo gariepensis eggs.
Fig. 8. The aggregating tadpoles of Bufo gariepensis.
The second species, the Common Platanna or African clawed toad (Xenopus laevis) [Fig.9] has webbed toes, and lacks a tympanum, tongue and movable eyelids as an adaptation for an aquatic life. Adults are both predators and scavengers. Their eggs are small, heavily pigmented and are enclosed in individual jelly capsules attached to submerged objects.
Fig. 9. The aquatic Platana, Xenopus laevis.
The question arises from whence these amphibians came? Because both species are indigenous over this vast and arid region, it can be surmised that they had buried themselves in the sandy banks of the dry streamlets in order to survive the adverse drought conditions. This phenomenon has been observed in the Namib Desert where frogs were found a metre deep in sand under a dried pool in dry-hibernation. Had the Tanqua floods not brought them to activity, they would not have been known to occur on the farm.
Honeybee races at hybrid zone
The Cape honeybee (Apis mellifera capensis) [Fig.10] is restricted to the winter rainfall region of southern Africa but is purported to have an interface with the Savannah bee (Apis mellifera scutellata) along the margins of this region which has been designated as the ‘hybrid zone’. Because the outer margins where the two honeybee races converge are mostly semi-desert, it has been postulated that the low numbers of wild colonies and the correspondingly reduced population pressure between the two sub-species, could result in co-existence but changes in the winter and summer rain could influence the success of a given species occupying the zone.
Fig. 10. The Cape honeybee, Apis mellifera capensis, the dominant sub-species on the farm.
Fig. 11. Apis mellifera scutellata visiting the flowers of Eberlanzia ferox.
Several other factors may also influence the habitation and cohabitation of the bees. The area where the highest numbers of ovarioles occur in laying-workers of the Cape bee is regarded as the ‘heart’ of the capensis distribution. This lies in an inverted triangle that can be drawn from Stellenbosch in the west, to Swellendam in the east, and to Cape Agulhas in the south. The Cape bee has maintained its dominance in the winter rainfall regions for many thousands of years. The predominance of capensis is also observed when scutellata hives are brought into their region. Within a few years such hives become occupied by capensis because capensis workers find their way into scutellata colonies and become laying-workers and eventually take over these colonies by becoming pseudo-queens. This is due to the higher level of queen pheromone possessed by the Cape bees.
The ‘Capensis Calamity’
Cape honeybees taken to the aloe-flow on the Springbokvlaktes north of Pretoria were able to infiltrate scutellata colonies during the manipulations which take place when ‘making increase’. This is accomplished by taking advantage of the massive amounts of pollen available by dividing a hive and allowing queens to be produced in the queenless brood placed above the queen excluder. Such conditions are ideal for the acceptance of a Cape bee into the queenless partition and here to rapidly develop into a pseudo-queen. The upper partition rapidly fills up with capensis brood and then Cape honey bees emerge.
Despite this proliferation, it appears that capensis colonies do not survive for long in the summer rainfall region but steadily dwindle in numbers and eventually die out. Cape bees rarely are able to invade healthy widely scattered natural colonies of scutellata, but will readily invade commercial colonies because of their proximity in apiaries where regular manipulation takes place. There is much anecdotal evidence that honeybees are adapted to certain environments where they flourish, yet merely maintain themselves when taken to a different environment. For instance, honeybee colonies hived in the Delmas area and brought to Pretoria where they were average producers compared to resident colonies, excelled when taken back to the sunflowers around Delmas each year. Cape bees in Pretoria were seen in greater numbers to visit Cape plants like vygies compared to scutellata bees. After more than 30 years in scutellata territory, other than as invaders of manipulated commercial scutellata hives, the Cape bee has failed to become established in the summer rainfall region.
Shifting boundary
In May 2023 on one of the hills on the Tanqua farm where the vygie Eberlanzia ferox was flowering, some bright yellow honeybees were found with little pubescence on their abdomens which could only be scutellata [Fig.11]. Had they temporarily expanded into capensis territory due to the excessive (summer) rains and the resulting mass flowering of plants which could facilitate such an expansion? Although the identity of the bees has not been determined scientifically by dissection, having worked with both races for many years it is possible to superficially identify the two races with some certainty. Perhaps the history of the region should give an indication.
History of the Tanqua Karoo
The farm is situated in the Tanqua Karoo, the name probably being derived from “Sanqua” indicating that the San were the first inhabitants of the region. There is also a river bed named the Tanqua. The region is also known as the ’Onder Karoo’ and ‘Ceres Karoo’. The Khoi subsequently moved into this area with their livestock and the competition for pasture and water resources became intense. This was before the days of the wind pumps and the extraction of subterranean water. The Trekboers expanded into the interior in large numbers in the 18th century. In the 1800s this was a contested area which existed between Touwsrivier in the south, to the Hantam Mountains in the north and the Roggeveld escarpment inland. It was only possible to farm small stock in this area if a farmer was able to move across the boundaries between the winter and summer rainfall area in different seasons – which still is pertinent today. Farmers still take their sheep down to the Tanqua Karoo in winter to escape the extreme cold of the escarpment. The demarcation between winter and summer rainfall regions is not a precise line but rather a shifting corridor in which there might be little rainfall in both the winter and summer months. This all-season rainfall corridor coincides roughly with the line of the interior escarpment. Sheep and goats could survive in the winter rainfall region during winter but could not remain there when it dried out and the heat became intense. They would be moved further inland onto the higher escarpment in summer.
This region is subject to cycles of excessive rain followed by drought which resulted in competition for grazing amongst the Trekboers, Khoi and San hunters. This became an area of continual conflict for about a century. An example of this conflict is a report by Field Sergeant Charl Marais in September 1779. Although a comprehensive record does not exist for the climate, flora and fauna, some information is available about the rainfall in the region. Historically, the years 1700 to 1704 were years of poor rainfall but normal rainfall returned in 1705. Heavy rains in 1706 caused a great loss of livestock. July 1715 was exceptionally cold and wet and was associated also with an unknown cattle disease which led to high mortality. A severe drought in 1800 was followed by substantial rainfall in the Roggeveld in 1803 with many flowing streams. But during 1805 an extreme drought was experienced in the Tanqua Karoo. In contrast, there is a record that in one year the summer rains were so widespread that they swept through the Karoo to the sea.
Fauna and Flora
Visiting this farm regularly throughout the years unveiled the effect of climate and weather on the ecology of the area. Nothing stays the same from year to year. An insect species which is prolific one year may disappear totally for a number of years before reappearing again when conditions are suitable. A good example is the emerald fruit beetle (Rhabdotissemipunctata) which can be found cavorting on the flowers of Vachellia karroo. Prior to the long drought they had been prolific but disappeared until V. karroo flowered again due to the heavy rains in 2022/3 [Fig.12].
Fig. 12. The emerald fruit beetle Rhabdotis semipunctata on Vachellia karroo flowers.
Botanists visiting the farm over a weekend were able to identify 98 species of plants – and many more have yet to be identified. Yet honeybees are rarely seen on flowers despite hours of hiking each day on the farm. However, they are desperate for water in the hot summer months and will visit artificial pools of water. Despite masses of vygies of various species flowering in spring, it is rare to see a single honeybee visiting them. It appears that the amount of forage in the worst month greatly influences the carrying capacity of wild colonies in an area. Honeybees have been observed visiting Haemanthus coccineus, Brunsvigia bosmaniae and various species of Asteraceae.
Fig. 13. Succulent Tylecodon wallichii plants in flower.
Many species of succulent plants appear to have niche pollinators, many of them solitary or sub-social bee species. Tylecodon wallichii produces an exceedingly long raceme which towers above the karroid scrub. It attracts a Xylocopidae (carpenter bee) species which flies from the one exposed flower stalk to the next which is clearly visible in the landscape as they project well above the karroid scrub [Fig.13]. There are also seven species of carrion flowers (Stapeliads) whose flowers produce a stench of either sweat, urine, faeces or a rotting cadaver by which they (deceptively) attract flies without any reward which pollinate them [Fig.14]. This makes at least a subset of plants independent of bees for pollination. The pollination of these plants is further amplified by the placing of all the pollen in a sac (pollinium) which the fertilising insect transfers. A similar strategy is employed by orchids, of which only one species has been found on the farm. The Gorteria diffusa uses a different strategy to attract insects. By expressing pigments on the petals, the spots which resemble insects, they attract the passing fly to visit the plant and it becomes a pollinator. Nevertheless, bees remain important for the pollination of some of the plants whether they flower in the summer or winter.
Fig. 14. The carrion flower, Hoodia pilifera var. pilifera which attracts pollinating flies.
Occupation of the region by humans has undoubtedly affected the ecology of the region; especially with continual occupation and the introduction of livestock. The farm has not had stock on it for 20 years (except occasionally those of the neighbours which find an opening in the fence) but there are resident rhebok, duiker, steenbok and three pairs of klipspringers. Baboons regularly pass through and leave a tell-tale of the chewed roots of Euphorbia rhombifolia [Fig.15].
Fig. 15. Chewed remains of the roots of a Euphorbia rhombifolia plant uprooted by baboons.
Game abounded in this region before firearms appeared. Colonel Robert Jacob Gordon in 1777 attested to the large number of lions in the Tanqua Karoo. Augusta de Mist (1803) also commented on the large numbers of lions, leopards and hyenas and was enthralled to see a flock of about 300 ostriches on the southern plain below the Rooiberg which forms the one boundary of the farm. The Bokkeveld in fact was named after the scattered herds of springbok which migrated from the interior into this territory at times. The only accommodation on the farm is an old ‘skeerhok’ (shearing shed) in which to sleep from which a beautiful view over the veld can be seen as the sun sets [Fig.16].
Fig. 16. Sundowners in front of the ‘skeerhok’.
There is no doubt that weather and climate have a large effect on honeybees which expand in strength and number of colonies in favourable years. During unfavourable times, the honeybees decrease in numbers and possibly abscond. Judging from trap boxes placed out each year in the Swartland, drought can drastically curtail the numbers of migrating reproductive swarms. The banded bee pirate, Palarus latifrons, occurs on the farm and there are also generalist arthropod predators such as the Asilidae robber-fly [Fig.17]. However, although honey badgers have a wide distribution across Africa they have not been observed on the farm.
Fig. 17. Asilid robber with a honeybee captured on the Tanqua farm.
The interesting observations over approximately two decades need further study before the extensive development of facilities to generate electricity by harnessing wind or sunlight overwhelm the area. The Perdekraal Oos wind farm is located within 10 km of the farm where the observations have been made. Several other developments are envisaged in the Renewable Energy Development Zone (REDZ). The environmental impact studies for this development and other developments under consideration in the region reflect relatively short periods of study and do not provide detailed information on the waxing and waning of the numbers of bees and their nests, the interaction of the capensis and scutellata bees as well as other related pollinators. It is likely that periods of more summer rain have temporarily favoured scutellata bees while the capensis bees can be viewed as the predominant inhabitants of this region. It is also evident that there is an interaction between the bees and flora as well as fauna, including the provision of nests by aardvark burrows.
Cape Point Cape bee sanctuary
Because of the high numbers of Savannah bee hives that were being brought within the natural Cape honeybee distribution area, there was a fear of a threat to the existence of the Cape bee. It was decided to found a sanctuary for the Cape honeybee where they would be protected from hybridization. A cursory survey was carried out in the proposed sanctuary of Cape Point in1980. On the recommendation that no honeybees were present in the area, a decision was made to introduce colonies of Cape honeybees. These were fortunately located within the ‘heart’ of the Cape bee distribution at Fernkloof (Hermanus) and De Hoop Nature Reserve and approximately six colonies were introduced.
Yet the Cape bee has always occurred in Cape Point – one of the oldest maps of the Cape Peninsula having a location named Bynes, alludes to this. Over the past 8 years of research in locating and analysing wild colonies in Cape Point, 98 wild honeybee nests were recorded – and more still have yet to be located. Then how was the incorrect assessment of the total absence of honeybees in Cape Point arrived at? It appears that there was one visit on a specific day only and a cursory search of bees on flowers was made. At certain times of the year in Cape Point, masses of various plants can be in flower but no bees are seen visiting them. Honeybees gauge which flowers are most cost effective and will visit those despite other species in full bloom. Also, the carrying capacity of an area appears to be determined by the level of resources available in the month(s) of dearth. Thus the timing and duration of the survey becomes of utmost importance if it is not to become a mere snapshot in time!
The pressure on development of the land and the changes in climate should compel us to document our unspoilt areas in detail, to perform comprehensive EIAs and to monitor the impact of the developments for all our flora, fauna and landscape.
Zig-zag emperor moth larvae, Gonimbrasia tyrrhea, on Vachellia karroo.
Brunsvigia bosmaniae.
Haemanthus coccineus growing out of a slope.
The authors: Geoff Tribe, A. David Marais & Karin Sternberg
Geoff Tribe
Dave Marais
Karin Sternberg
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