Eristalis tenax

Species of fly

Eristalis tenax, the common drone fly, is a common, migratory, cosmopolitan species of hover fly. It is the most widely distributed syrphid species in the world, and is known from all regions except the Antarctic. It has been introduced into North America and is widely established. It can be found in gardens and fields in Europe and Australia. It has also been found in the Himalayas.

The larval form of the drone fly, the rat tailed maggot, is found on every continent except Antarctica, and ranges to the highest latitudes in the North.

Eristalis tenax is a large, stocky bee mimic. The eyes are marbled in black. Males have hovering displays. The average wing length is 9.75–13 mm and their average wingspan is 15 mm. The exact appearance of the drone fly can vary considerably. The abdomen can vary in color from dark brown to orange. Research suggest that male drone flies live in the same territory their entire lives. When away from its "home territory", a male drone fly rarely responds to other insects. especially in late summer and autumn, and can be significant pollinators. They often feed on the flowers of carrot and fennel. Under extremely rare conditions, there have been documented cases of human intestinal myiasis of the rat tailed maggot (larva of Eristalis tenax). Zumpt proposed a hypothesis called "rectal myiasis". During open defecation in the wilderness, flies attracted to feces may deposit their eggs or larvae near or into the anus, and the larvae then penetrate further into the rectum. The larva can survive, feeding on feces at this site, as long as the breathing tube reaches out from the anus, which is quite rare.

The common drone fly is reported to have caused accidental myiasis. In humans, myiasis can be caused in four ways: intestinal or gastric, nasal, auricular, or anal. The larvae are usually found in still or stagnant water, like water reservoirs or liquid dung.

Pupation happens in a drier location than where the larvae develop.

It was found by researchers that when E. tenax accidentally traps pollen among the body hairs, the pollen grains are combed off by the front and hind tibia, and transferred to pollen retaining bristles on the front and hind tarsi. The pollen grains that are retained among the front tarsal bristle are eaten directly from the bristles.

There is little doubt that the morphological and behavioral similarities between E. tenax and the honey bee are mainly a result of convergent evolution in response to similar food gathering requirements.