Stingless “Mopane” Bees of Southern Africa

(Commonly but incorrectly called “Mopane Flies”)

Introduction

Across the savannas and woodlands of southern and central Africa, visitors frequently encounter tiny insects that hover persistently around the eyes, nose, and mouth, especially on hot days. These insects are widely misidentified as “mopane flies.” In reality, they are stingless bees, not flies or gnats but a diverse and ecologically important group of true bees within the family Apidae.

Far from being pests, stingless bees are highly sophisticated social insects and vital pollinators in African ecosystems. For safari guides, understanding these bees allows for accurate interpretation and reassurance of guests. (Despite their persistence, they cannot sting and do not bite.)

Scientific Classification

• Family: Apidae
• Subfamily: Apinae

Southern Africa is home to eight species of stingless bee, in five genera:

• Hypotrigona
• Meliponula
• Liotrigona
• Cleptotrigona
• Plebeina

Two species are especially well known:

• Hypotrigona gribodoi – one of the most frequently encountered stingless bees in Zimbabwe, Zambia, Botswana, South Africa, and parts of East Africa
• Plebeina armata (used to be called Plebeina hildebrandti) – commonly called the mopane bee or mopane “fly,” the sole member of its genus

Distribution and Habitat

Stingless bees are widely distributed across southern and central Africa, including South Africa, Botswana, Namibia, Mozambique. Zimbabwe, Zambia and the D.R.C., all the way up to Uganda and Rwanda.

They are particularly common in hot, dry regions, explaining their frequent association with mopane trees (Colophospermum mopane) and the origin of the misleading name “mopane fly.”  They in fact inhabit a variety of environments from riverine forests through mopane and miombo woodlands to savanna and bushveld. Ecologically, they are important generalist pollinators, contributing significantly to plant reproduction and ecosystem stability.

Appearance, Identification and Comparison with Honeybees

. Key identification features include:

• Very small size (typically 2–4 mm, up to 5 mm in Plebeina armata)
• Black to dark brown body
• Slender shape with narrow, clear wings
• Fast, darting flight

Stingless bees are often mistaken for flies or gnats due to their size and behaviour. Closer inspection, however, reveals clear bee characteristics such as elbowed antennae.

Comparison of Stingless Bees and Honeybees (Apis mellifera)

Stingless bees are true bees, like honeybees, but they cannot sting and they use resin as well as wax to build their nests. Both types:

• Are social
• Make honey
• Live in long-lasting colonies
• Nest in natural cavities (in trees, termite mounds, ground, rocks)
• Play an important ecological role as pollinators

The following table highlights the differences between stingless bees and honeybees.

Feeding Habits and Honey Production

Adult stingless bees feed on a wider range of plant materials than honeybees including nectar, pollen, plant sap, fruit juices, plant resins and honeydew (a sweet, sticky substance excreted by insects like aphids, scale insects and cicadas and often deposited on leaves and stems).

Through these feeding activities, they play a critical but often overlooked role in:

• Pollinating indigenous trees and shrubs
• Maintaining woodland and savanna plant diversity
• Supporting ecosystem health

Stingless Bee Honey

The honey produced by stingless bees is stored in resin pots in the hive (not wax combs). Yields are small and the honey is rare. It is darker and more liquid than honeybee honey and often sour or tangy in taste.

This honey has great cultural importance and is highly prized and considered a delicacy. It is used in traditional medicine and is believed to have antibacterial and healing properties.

Rural communities sometimes harvest nests for honey and pollen, though this can threaten colonies if done unsustainably.

Social Life, Colony Structure and Founding

Stingless bees are truly social insects. Colonies consist of:

• A single queen;
• Numerous worker females;
• Occasional male drones. Male stingless bees feed themselves at flowers and may even perform some colony tasks such as feeding the larvae and cleaning the nest;
• Colonies may persist for many years if undisturbed.

New colonies are founded when a virgin queen absconds from the natal nest accompanied by a large group of workers. Swarming is infrequent, probably because suitable nesting cavities are scarce.

The queen releases pheromones that attract hundreds of males, though she mates with only one.

Nest Sites

Stingless bees nest in sheltered cavities, including hollow tree trunks and branches, cavities in termite mounds, rock crevices and occasionally in man-made structures such as walls or pipes.

Ground-nesting Plebeina armata have colonies numbering 3,000 to 10,000 individuals. Nests are located about 650mm below ground in cavities that are often abandoned termite nests.  (Cases have been recorded where a stingless bee colony has shared the space of an active termite mound.)

The tree-nesting Hypotrigona gribodoi are in colonies of 500-800 individuals. They appear to nest preferentially in certain tree species in different regions. In KwaZulu-Natal, for example, they have been recorded to prefer cavities in dead wood of tamboti trees, Spyrostachys africana, whereas in Limpopo Province of South Africa they use red bushwillow trees, Combretum apiculatum.

Nest Construction and Layout

Construction material: Nests are constructed from a material called cerumen, a durable mixture of wax (produced by a dorsal gland, like honeybees), plant resins and sometimes other plant material and mud. Cerumen is much more pliable than the pure wax that is used for cell building by honeybees. The wax is stored in wax deposits in the nest. The resin is collected fresh from preferred host plants, attached to the corbiculae (“pollen baskets” of the bee) as with pollen, and then stored in resin deposits in the nest until needed. Consequently, there is always a ready supply of building materials available in the nest.

Entrance: The nest has a small tubular entrance hole, often guarded by workers. Tree-nesting Hypotrigona gribodoi have a single narrow nest entrance tube (4 to 7mm in diameter and 20 to 200mm long) that extends only to the edge of the nest cavity.  Ground-nesting Plebeina armata have a single, sticky resinous tube that projects a few centimetres above the ground and provides the only access to the nest.

Storage: Honey and pollen are stored in separate spherical “pots,” rather than hexagonal combs.

Brood chamber: In stingless bees brood is produced in a similar manner to most solitary bees (as opposed to honeybees). (In beekeeping, “brood” refers collectively to the immature life stages of bees found within the cells: the eggs, larvae, and pupae.) An egg is placed on top of a food mass in a cell, then the cell is sealed. Honey and pollen are stored in separate ‘pots’. Brood cells are round or ovoid and food storage containers are small to large spheres.

Nest Climate Control, “Breathing” and Defence

Because they are accessed through a single narrow entrance tube stingless bee nests are almost entirely water-tight and airtight. This design offers excellent protection from predators and insulation but also creates challenges for ventilation and moisture control.

• Ventilation: The airtight nature of the nesting cavity and its single entrance tube create difficulties in regulating the concentration of respiratory gases in the nest as the entrance tube is the only route for fresh air to enter and stale air to exit the nest. Both ground and tree nests have similar problems with the build-up of stale air from bee respiration and brood metabolism. This requires special ‘respiratory’ behaviour on the part of the colony inhabitants.

Both types of nests ‘breathe’ in a manner similar to that of a mammal. This colonial breathing is not the result, however, of synchronised individual bee breathing but rather by bees fanning their wings. Their fanning expels stale air and creates a corresponding small drop in pressure inside the nest cavity, which results in the passive entry of fresh air from outside.

• Temperature control: In the soil-nesting Plebeina armata, breathing pulses are more frequent and air volumes pulled in smaller during daytime than at night which is probably a response to the hot outside air.

Research by Robin Crewe (University of Pretoria) revealed colonies regulate temperature despite extreme external heat:

– Plebeina armata nests maintain 32 °C even when soil temperatures exceed 60 °C

– Hypotrigona gribodoi nests remain around 35 °C regardless of ambient conditions. (Tree-nesting species, because of their generally shaded nest positions and the insulating properties of the surrounding wood, experience more moderate ambient temperatures.)

• Moisture control: In ground-nesting species, special drains made of the same material as the entrance tunnel are constructed to lead away excess water that builds up in the nest from condensation. Workers of arboreal species, on the other hand, imbibe excess water droplets in the nest, then carry and eject them outside.
• Nest Defence: The bees defend the nest, mostly against ants, by placing sticky resin droplets near or in the entrance, or by blocking the entrance with large resin balls.

Interaction with Humans

Stingless bees are often attracted in considerable, irritating, numbers to people who are active outdoors on hot, sweaty days, particularly to:

• The moisture around eyes
• Sweat
• Moist mucous membranes in the nostrils

These fluids provide essential water, salts, proteins and minerals in dry environments. Eyes are particularly attractive because they remain moist even in extreme heat. This behaviour has earned Plebeina armata the nickname “sweat bee.”

They are not aggressive and they are not seeking blood. They do not:

• Bite
• Sting
• Damage eyes

. Although harmless, they can be irritating when present in large numbers. It might help to wear sunglasses, to stay calm and avoid frenzied swatting at them and to move into shade or a place with a breeze.

Conclusion

The insects commonly misnamed “mopane flies” are, in fact, stingless bees – highly evolved, social pollinators essential to African ecosystems. Their unusual behaviour around people, sophisticated nest engineering, and valuable honey make them a fascinating subject for interpretation.

For guides, understanding stingless bees transforms a common annoyance into an opportunity for education, reassurance, and deeper appreciation of the complexity of the African bush. Even the smallest creatures, it turns out, play an outsized role in sustaining life.

SOURCES

Chakuya, E. & Gandiwa, N. Mubuko & V.K. Muposhi, A Review of Habitat and Distribution of Common Stingless Bees and Honeybees Species in African Savanna Ecosystems, Researchgate, ResearchGatehttps://www.researchgate.net › … › Stingless Bees, May 2022

iNaturalist, Photos of Mopane Stingless Bee Plebeina armata

Picker, M, C. Griffiths & Alan Weaving, Field Guide to Insects of South Africa. Struik Publishers, Cape Town:2002

Scholtz, C. & J. Scholtz,& H. de Klerk, Pollinators, Predators & Parasites. Struik Nature, Cape Town:2021

Wikipedia, https://en.wikipedia.org › wiki › Stingless_bee

Weaving, A., Insects: A Review of Insect Life in Rhodesia, Regal Publishers, Salisbury:1977