Many types of flies have evolved to look remarkably similar to bees. This phenomenon represents a natural survival strategy, where harmless flies gain protection by imitating the appearance of stinging bees.
Understanding Mimicry
The resemblance between certain flies and bees is a prime example of Batesian mimicry, a defensive strategy where a harmless species evolves to imitate a dangerous one. This allows the mimic to deter predators that have learned to avoid the dangerous model. Bees, equipped with a painful sting, are often avoided by predators like birds and reptiles.
Flies that cannot sting benefit from this association; a predator that has previously encountered a bee and learned to avoid its sting will likely steer clear of a bee-mimicking fly as well. This mimicry provides an evolutionary advantage, enhancing the mimetic fly’s chances of survival. Through natural selection, traits that make flies look more like bees become more prevalent in the population over generations.
Flies That Look Like Bees
Many fly species display convincing bee mimicry, often with yellow and black striped bodies. Hoverflies, belonging to the family Syrphidae, are common bee mimics. These flies often resemble honeybees or bumblebees, with some species even mimicking the buzzing sound of bees. Drone flies, a type of hoverfly, mimic honeybees in appearance and flight patterns.
Bee flies (family Bombyliidae) are another group known for their bee-like appearance. These flies typically have stout, hairy bodies that can resemble brown carder bumblebees or male hairy-footed flower bees. Their long proboscis, used for feeding on nectar, can sometimes be mistaken for a stinger. Some parasitic flies (family Tachinidae) also mimic bees, with species like Tachina grossa resembling large black bumblebees.
How to Tell Them Apart
Distinguishing between a bee and a bee-mimicking fly involves observing several key physical and behavioral differences. One of the most reliable indicators is the number of wings: flies possess only one pair of wings, while bees have two pairs, though these can be difficult to discern when folded. Another clear difference lies in their antennae; flies typically have short, stubby antennae that are often difficult to see, whereas bees have longer, more prominent, and often elbowed antennae.
The eyes also offer a clue: flies often have large, compound eyes that can cover most of their head and sometimes meet at the top. In contrast, bees have more distinctly separated, oval-shaped eyes positioned on the sides of their heads. Body shape varies as well; flies tend to have a thick waist where the thorax meets the abdomen, without the distinct narrow constriction often seen in bees. While many mimicking flies are hairy, bees generally have more abundant, branched body hair, particularly on their legs, which helps them collect pollen. Flies also exhibit a characteristic hovering or darting flight pattern, whereas bees tend to have a more direct flight path.
Beyond the Disguise
Bee-mimicking flies play important ecological roles. Many hoverflies, for example, are significant pollinators, visiting flowers to feed on nectar and pollen, much like bees. While they may not always be as efficient as bees, their contribution to plant reproduction is notable.
The larvae of many hoverfly species are beneficial predators of common garden pests, such as aphids, providing a natural form of pest control. These flies are entirely harmless to humans, as they lack a stinger and cannot bite. Their mimicry is purely a defensive strategy, allowing them to exist without the need for actual defensive capabilities. Recognizing their ecological benefits helps appreciate their presence.