Eristalis tenax

Eristalis tenax is a hoverfly, also known as the drone fly (or 'dronefly'). Eristalis tenax is common, migratory and cosmopolitan, 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 all over both Europe and Australia, but have also been found all the way up in the Himalayas. Eristalis tenax is a large (wingspan 15mm), stocky, bee mimic. Eyes are marbled in black. Males have hovering displays. External imagesFor terms see Morphology of DipteraWing length 9·75–13 mm. Stout appearance. Femur 3 thick, hanging down while hovering. Antennomere 3 brownish-black. Tergite 2 with yellow, orange or reddish side-markings. Arista bare. Eyes brown-haired, with two distinct bands of dense and darker hair. Male eyes clearly holoptic. All tarsi black. The male genitalia are figured by Hippa et al. (2001) The larva is figured by Hartley (1961) and in colour by Rotheray (1993). Larvae are saprophagous. The larva of E. tenax is a rat-tailed maggot. It lives in drainage ditches, pools around manure piles, sewage, and similar places containing water badly polluted with organic matter. The larva likely feeds on the abundant bacteria living in these places. When fully grown, the larva creeps out into drier habitats and seeks a suitable place to pupate. In doing so it sometimes enters buildings, especially barns and basements on farms. The pupa is 10–12 mm long, grey-brown, oval, and retains the long tail; it looks like a tiny mouse. The adult fly that emerges from the pupa is harmless. It looks somewhat like a drone honey bee, and likely gains some degree of protection from this resemblance to a stinging insect. The adults are called drone flies because of this resemblance. In its natural habitat, E. tenax is more of a curiosity than a problem. Like other hover flies, they are common visitors to flowers, especially in late summer and autumn, and can be significant pollinators. They mainly feed on 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. They can survive feeding on feces at this site, as long as the breathing tube reaches towards the anus which is quite rare.