Lesser housefly

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July 1, 2003

By: Dr. Kyle Jordan

Species: Fannia canicularis

Order: Diptera

Family: Muscidae

The lesser housefly (LHF) is a nonbiting fly found throughout the United Sates. It is in the same family as the common housefly (Musca domestica), and is considered to be one of the “filth flies.” They look fairly similar to Musca and have similar life cycles, but are still different enough that it is important to be able to tell them apart.

 

Generally, the LHF appears earlier in the year than M. domestica, reaching its largest numbers in early summer and again in late fall. The body of the adult LHF is smaller than that of the common housefly, and the abdomen is leaner. The LHF also has three faint stripes on the dorsal surface of its thorax (the stripes on the common housefly are more pronounced). Upon close examination of its wing venation, the fourth vein continues straight to the edge of the wing, whereas the vein of M. domestica is sharply bent.

LHF tend to fly in circles, especially around objects such as hanging lamps, fans and people standing in the middle of a room. When they land, they seem to prefer vertical surfaces, and will often land on suspended cords or chains.

The entire lifecycle of a LHF may take 15 to 30 days to complete. The banana-shaped eggs hatch two days after they are laid in semiliquid organic matter such as animal or human excrement. LHF larvae have flattened, fleshy extensions along the side of the body.

In about a week, the larvae will pupate. The pupal stage takes another week. The pupa is concealed in a dark reddish-brown pill-shaped puparium, a hardened case that protects the vulnerable fly until it emerges.

The female LHF deposits eggs two to five days after she emerges and will remain in the general area where she oviposits. Males, on the other hand, may migrate quite a distance from the site where they emerged. Adult flies live for about two months.

The LHF is significant because it can be a major pest, especially near chicken farms where it breeds copiously in manure. They are associated with spoilage of food, annoyance, mechanical transmission of pathogens and accidental myiasis (infestation of the human body by fly larvae). The most significant of these is annoyance – flies may enter homes and barns in large numbers.

Though it is possible for the LHF to transmit pathogens such as salmonella, shigella, pinworms and tapeworms, successful transmission by the LHF is not very likely (less likely than for M. domestica, actually, which has a much closer association with humans). 

Treatment Methods

There are two types of myiasis with which the LHF are associated:

1. A female may oviposit in an open wounds or sore, under the impression it would be a viable source of nourishment for her offspring.

2. If food is left out and a female oviposits on it before it is ingested, the ingested larvae can develop in a person’s digestive tract. This is documented mostly from cases involving overripe fruit.

These flies are not parasitic, however, and any case of myiasis involving this fly is accidental. Furthermore, no fly has a lifecycle that involves being ingested by a human.

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