Bee Flies have pubescent (hairy) bodies and long, slender legs. The proboscis is long, points forward, and is adapted for feeding on flower nectar. I most often see Bombylius major (fig.1) nectaring at dandelion in early spring, a flower that seemingly does not need such a long proboscis. It may be that the flowers with long corollas upon which these flies fed during their long evolution have gone extinct, or are merely absent from Chicago suburban environs. Bee flies, like the diurnal clearwing moths rarely actually come to rest on a flower while feeding. At most, they dangle their front legs against the bloom, one assumes for balance and stability. This is probably in defense against (usually very well-camouflaged) predators such as crab spiders (family Thomisidae) and ambush bugs (family Phymatidae) that lie in wait at flowers. Eggs are laid near the entrance to the nest of the specific bee host parasitized by that species of bee fly. The tiny larvae enter the nest and usually wait until the bee larva has pupated before metamorphosing from a small, mobile animal to a smooth, fat larva which feeds on the bee pupa. The bee fly pupa is dual-phased. The first pupa is ‘normal’; the second stage has a sharp battering ram with which to break down the nest cell wall, made by the adult bee when closing the cell.

Bee Fly, Poecilanthrax willistonii. Photographed near Newspaper Rock, Canyonlands National Park, Utah.

Bombylius major

Bee flies are stout-bodied flying insects said to resemble long-legged bumble bees, but I've never seen that connection. There are Syrphid flies and robber flies that do a much better job of impersonating bumble bees. Many bee flies have elongated mouthparts that form a conspicuous beak, used for sucking nectar long-distance while hovering over flowers. Bee flies much prefer to hover in midair while doing their nectaring, undoubtedly to avoid capture for those who lurk about flower blooms looking for an easy meal, such as the ambush bugs and the crab spiders. Adult bee flies become active about the third week in April, here in northern Illinois.

I most often see bee flies hovering around flowers, or if resting, usually on the ground, on bare soil. They are extremely wary and difficult to approach. No doubt their large compound eyes give them good vision, plus they have that air-motion sensing mechanism that helps the ordinary house fly avoid the swatter. Adult bee flies drink nectar, but the larvae are parasites of beetle larvae as well as the brood of solitary wasps and bees, the hole or burrow-nesting insects. I've often seen female Bombylius sitting in very loose soil, vibrating her butt like mad, so that the dirt is actually thrown outwards (see our Bombylius major pictures). One source says these flies are "gathering sand to coat their eggs", ostensibly to keep them from drying out. Uhm.. ok.

Many bee flies have boldly patterned wings, but it's their shape that generally tips me off that a specimen is in the Bombyliidae family. The shape is reminiscent of the best swept-wing fighter jets. The relatively short and usually pointed antennae are another clue, along with, of course, that dangerous-looking beak. Good thing these flies don't bite or sting. All in all, a fascinating insect worthy of study. Next springtime, why not take a trip to the woods? You'll find these gals busily gathering nectar from the dandelions along your favorite sunny path. Just watch out for the dog poo.

Figure 1. Large, forward-looking compound eyes and a long proboscis for sucking down nectar, Bombylius major

Lepidophora lepidocera

Bombylius major

Systoechus vulgaris