Numerous collections of adults show their attraction to odors: they have been caught in a hospital laboratory and an operating room, in latrines, near sewage, and in septic tanks in a Dairy Cheese room and in a butcher shop. A huge number has been collected dead in a plastic about trunk containing Cannabis sativa (Sabrosky 1983). Other specimens were observed to congregate on small fruit of Calotropis procera and on Mormordica charantia (Deeming 1998).
The larvae of D. varipalpis develop in bio-filters, e.g. sewage filters, in dung, and in diverse kinds of decaying vegetables or fruits (e.g lettuce, potatoes, sugar beet roots, blue figs, pomegrantes, melons, pumpkins. Occurance on various planes and ships suggests the probable importance of commerce in the distribution of varipalpis (Sabrosky 1983).
They were found breeding in enourmous numbers in a vermiculite-alfalfa meal-brewers' yeast mixture used as a breeding medium for eye gnats in California. Other records include the adults living around and depositing their eggs on a fungus growing on formerly preserved and dried sheep hearts in Texas (Sabrosky 1983) and the larvae living in close association with bacterial decay of the giant saguaro cactus (Santana 1961).
I. Brake has identified specimens collected on Tamarix and Ochradenus baccatus.
Polished spot on anepisternum small, fronto-orbital plates relatively broad, male palpus strikingly elongate, fusiform. (Sabrosky 1983)
Color: Black, heavily gray microtomentose; gena yellowish in ground color; antenna with scape and pedicel almost always reddish, contrasting with black basiflagellomere; palpus partly yellow, extensively so in the enlarged palpus of male, yellow on proximal half in female; knob of halter yellow; mid and hind tarsi yellowish except distal 2, rarely 3, tarsomeres (Sabrosky 1983)