Thursday, January 22, 2009

Mystery Bot Fly

Several month ago, the fly shown in the images landed in the office at the Audubon Center at Francis Beidler Forest. Having never seen anything like it and being unable to identify it, we captured it in the name of science. We've narrowed the identification down to the genus Cuterebra, but we are not yet sure of the species. Based on the number of Gray Squirrels (Sciurus carolinensis) we have seen with warbels (the lumps [a.k.a.bots or wolves] that house the larvae as they feed on the host), we supect our specimen is Squirrel Bot Fly (Cuterebra emasculator).

Our specimen appears to be a female based on what looks like an ovipositor at the base of the abdomen. We're still trying to track down a resource on bot fly anatomy! The female does not deposit her eggs within or on the host. Instead she deposits her eggs in an area likely to be visited by the desired host. It isn't known how she determines this, but when a host brushes by, the egg is picked up. When a larva emerges from the egg, it will burrow into the host's skin forming the bot. It is unknown how great an infestation is required to cause health stress for the host or for young, if a nursing female host is involved. The larva remains hooked inside the host as it feeds until it emerges through its breathing hole and drops to the ground in which it will burrow and pupate.

Most bot flies have a specific wild animal host that they target, but humans and domestic animals can occasionally become hosts. In Central America, the bot fly, Dermatobia hominis, targets humans. If you don't like the sight of a palmetto bug, you would have a hard time dealing with Dermatobia hominis.

Although we're sure our specimen is not Dermatobia hominis, we would like to make a species-level identification. Please contact us if you can make such an identification.

Images by Mark Musselman

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