The larvae of the little house fly are distinctly different from the white, tapered, cylindrical larvae of the house fly.
The Fannia larva is rough, brown, flattened dorsoventrally, abruptly narrowed anteriorly, and has many well-developed plumose lateral and dorsal processes on each segment after the first.
There is one pair of anterior prothoracic spiracles, each with 3–12 short processes arranged in a radial fashion. The posterior spiracles are raised on short, stout stalks. There are well-developed mouth hooks. The larvae develop through three instars. The larvae of species of Fannia which may occur in animal manure all conform to this general description.
To distinguish among the species it is necessary to examine closely the lateral processes and other characteristics, especially in the posterior region.
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Details of posterior segments of Fannia larvae.
A. Dorsal view of Fannia canicularis.
B. Dorsal view of Fannia scalaris.
C. Dorsal view of Fannia femoralis.
D. Dorsal view of Fannia pusio.
E. Ventral view of Fannia canicularis.
F. Ventral view of Fannia scalaris.
G. Ventral view of Fannia femoralis.
H. Ventral view of Fannia pusio.
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Larvae of F. scalaris resemble the larvae of F. canicularis but the lateral posterior processes of scalaris are more plumose and have a shorter terminal portion than canicularis.
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