Bee flies are a fairly large family of true flies; they are not bees and they do not sting or bite. Most resemble pudgy, fuzzy bees, while others look like strangely fuzzy mosquitoes, having a long proboscis (straw-like mouth tube, with which bee flies suck fluids such as nectar from flowers). Bee flies' habit of hovering also makes them look beelike.
Like other flies that are bee mimics, bee flies can be identified as flies by their single (not double) pair of wings, their very short antennae, their softer bodies, and their large, compound, "fly" eyes that often nearly touch. They are hairy, usually stout-bodied, often brightly colored, with many resembling bees or wasps, though many species are dark or speckled. The wings usually have dark markings. At rest, the wings are typically held out to the side at about 45 degrees, forming a triangular shape. The legs are slender. Mouthparts vary; some are short and broad-tipped; other species have a long tubelike proboscis.
Similar species: There are many groups of true flies (such as the syrphid family), that are bee or wasp mimics, and several other insects, including moths and beetles, look like bees, too. Also, there are many species of actual bees and wasps, as well!
Length: ¼ to 1¾ inches (varies with species).
Habitat and Conservation
As with most insects, bee flies are usually found in places where their food sources are abundant and where suitable egg-laying sites are available. Bee fly adults are therefore often seen as they visit flowers in fields, prairies, gardens, and so on. Adult females are often seen hovering in places where their hosts probably have nests, and this varies widely according to the host species. If the bee fly larva eats the larvae of a burrowing species such a tiger or long-horned beetles, the mother bee fly hovers over the ground or on decaying trees near those burrows. As another example, the tiger bee fly (Xenox tigrinus) parasitizes the nests of carpenter bees, so female tiger bee flies are often seen hovering near wooden structures where carpenter bees have excavated their nests.
Adults are often seen feeding on pollen or nectar from flowers, especially members of the sunflower family such as coneflowers and asters. Some prefer lilacs or apple or plum blossoms. They often feed while hovering, without perching on the flower itself. As larvae, the many different species of bee flies feed on a variety of host eggs or larvae, including many kinds of beetles; moths; flies; grasshoppers, katydids, and other orthopterans; bees and wasps; antlions; and even ichneumons, tachnids, and other insects that are themselves parasitic on other insects!
Bee flies are a family of true flies and are not bees at all. Lacking the ability to sting or to bite, their bee mimicry helps them avoid many would-be predators. The bee fly species that have a long, pointed proboscis (beak) do look pretty imposing, however.
Bee flies have a fascinating variation on the typical full-metamorphosis insect life cycle; most of them undergo hypermetamorphosis. The mothers deposit (or sometimes fling) their eggs onto or into their specific host insect's nest cavities. The first, youngest stage of the bee fly larva is quite active and moves around, makes it way to the host larva or eggs, attaches itself to the host, then in subsequent stages the larva is a quite sedentary maggot, feeding off its host. It pupates, exits the host's nest, and becomes a mature winged adult.
Of course, it is easy to fear bee flies, since they look like they could inflict a painful bite or sting. But bee flies should be appreciated for their role in reducing the potential numbers of truly problematic insects such as cutworms, armyworms, carpenter bees, and grasshoppers.
People have only started to understand the complex interactions among plants and insects, and among insects and other insects. It is rather mind-blowing to think that the larvae of some types of bee flies eat the larvae of species (such as ichneumons or tachnids) that eat the larvae of still other species (such as beetles or moths)!