Identifying flies and bees: so many similarities, but some big differences

To Be a Bee or To Be a Bee Fly? Differentiating Bees from Flies Copyright Thomas L Webster. All rights reserved.

"Summertime and the imaging is easy...Flies are flyin' and bees are a buzzin'...Oh, the Velvia's rich and your images are good lookin'...So hush, little photographer...Go out and give it a try!" OK, George and Ira Gerschwin I'm not! Invariably the question will be asked about a flying critter, "Is this a fly or a bee?" Nature, in all her glory, has seen fit to create a myriad of insects that mimic one and another, especially when it comes to flies and bees and wasps. By now, we are all familiar with syrphid flies that look like yellow jacket wasps and robber flies that mimic bumble bees. But, how can we be sure? What follows is a discussion of the major characteristics that will help our members differentiate between flies, bees, wasps, and flying ants. As always, there will be exceptions to some of the listed characteristics but, the characteristics taken as a whole for the particular orders, will be accurate. (Hint: Never base an ID on a single characteristic. For example, mayflies have only 2 wings, too.) Fly characteristics will appear in the left column and bee/wasp/ant characteristics will appear in the right column. Order Diptera   Order Hymenoptera Syrphid Fly Wing   Bumble Bee Wing Order Diptera (Flies)...Diptera (di--two; ptera--wing) literally means "2 wings". This is, indeed, the easiest characteristic to use to differentiate a fly from a bee, wasp, or flying ant. What would normally be a hind wing becomes a reduced appendage called a "haltere". The halteres do not resemble a typical wing. The halteres are instrumental in the equilibrium of the fly while flying. Don't mistake the "calypters" for halteres. The calypter is a part of the front wing.   Order Hymenoptera (Bees, Wasps, Ants)...Hymenoptera (hymen--union; ptera--wing) refers to the union of the front wing with the hind wing in flight. The leading edges of the hind wings have hooks, "hamuli", that catch the trailing edges of the front wings. The major characteristic to note, here, is that bees/wasps/flying ants have 4 wings. The hind wing is smaller than the front wing and can be greatly reduced in size. However reduced in size, the hind wing will always look like a wing. Calliphorid Fly Head   Golden Wasp Head A close examination of a fly's head will reveal several identifying characteristics. Typically, a fly's antennae are short and club-like. There are exceptions in which the antennae may be long, and many segmented but those species are fairly rare. Only flies have "aristae" (bristles) that arise from the antennae. Some flies, such as mosquitos and gnats, can have very long, bristly antennae that make the antennae look like miniature ostrich plumes. These antennae are said to be "plumose". Flies have true bristles on their heads and bodies. Bristles are stout, tapering hairs. Flies, bees, and wasps can have fine, short hairs covering their heads and bodies but, between Diptera and Hymenoptera, only flies have true bristles. The eyes of a fly pretty much dominates the head. The fly's eyes are more hemispherical in shape than a wasp's eyes or a bee's eyes. Some flies have such large, domed eyes that the eyes will touch, or nearly touch, at the top of the head. Of course, as stated before, there may be exceptions. All flies have a proboscis (not illustrated) which they can extend. The proboscis is formed by the fusion of mouthparts and also contain a tongue. Flies do not have jaws. The "bite" of a fly is actually the proboscis piercing your skin.   I've chosen a golden wasp head for a typical Hymenoptera head. It should be readily apparent that a bee's, wasp's, or ant's head lacks bristles. Hymenoptera may be covered head to anus with fine, short hairs (see honey bee leg, below) but Hymenoptera will lack true bristles on the head. Ants may have hairs in thick or thin numbers which superficially look like bristles but they are, indeed, hairs. Also, the antenna can be quite variable. The antennae are generally multi-segmented and longer than those found on flies. Many parasitic wasps may have thin, multi-segmented antennae as long as their bodies. Unlike flies, many Hymenoptera have jaws and can deliver a nasty bite! The jaws move side-to-side. Most wasps, carpenter bees, and leaf-cutting bees have jaws that cover a proboscis (not illustrated) with tongue. Nectar gathering Hymenopters, honey bees and bumble bees, for example, do not have jaws but have a protrusible proboscis. The proboscis is long enough to reach nectar at the bottoms of deep flowers. In most species of Hymenoptera the eyes do not dominate the head. Rather than being dome-like, typical Hymenoptera eyes are somewhat compressed laterally. Rarely are the eyes of a bee or wasp large enough to meet on the head. Ants, on the other hand, have greatly reduced eyes. Flesh Fly Foot   Honey Bee Hind Leg A third characteristic to observe are the insect's feet and legs. For the majority of fly species we normally encounter the feet will have pads (pulvilli) that allow flies to crawl on smooth objects in addition to tarsal claws. Between the tarsal claws there may be an "empodium". The empodium may be a single bristle or may look like another pulvilli. Not all flies have these but most do. Wasps, bees, and ants will not have these pads.   Bee, wasp, and ant legs will never have an empodium and pulvilli. Very seldom will there be hairs attached between the tarsal claws. There may be hairs, however, that extend from the last tarsal segment. Flies will never have pollen baskets. Some flower-feeding flies may become coated with pollen but flies lack the mechanism for compacting pollen into a tight package.   Here's a little test...You photograph an insect with 2 short antennae, large hemispherical eyes, 2 wings, and 2 long, fine tails? A fly, right? Wrong! A mayfly. Flies will have halteres and never have tails! OK, maybe that wasn't fair but always look the insect over carefully to make sure you see all of the key characteristics before committing to an identification. With the key characteristics, outlined above, you should not have any difficulty separating the majority of the flies from bees, wasps, and ants. Copyright Thomas L Webster 2005. All rights reserved.