The genus Musca is most commonly represented by the house fly, Muscadomestica. The adult fly feeds on various food stuffs through the use of its sponging mouthparts (Figure 5-51), and it will just as readily feed on feces and garbage as upon food consumed by cats or their owners. The larval stage, the maggot, is commonly seen developing in garbage, feces, and other decaying animal and vegetable material. The pupal stage is found in slightly drier areas around the site of larval feeding. The feeding process of the fly, whereby there is regurgitation of recently imbibed food along with saliva that aids in the liquefaction of the surface of the material being ingested, makes the fly an excellent means of transferring microorganisms from one site to another.
The fact that the nematode Thelazia has been reported from the eyes of cats would indicate that Musca or Musca-like flies, e.g., Fannia or Phortica spp., are feeding around the eyes of cats. In this case the larval stage leaves the mouthpart of the fly while the fly is feeding on lachrymal fluids. Gardiner et al. (1983) reported on a case of visceral myiasis that they believed due to Muscadomestica; it is possible, hoever, that they wree dealing with small larvae of a Cuterebra spp.
Gardiner CH, James VS, and Valentine BA. 1983. Visceral myiasis caused by Muscadomestica in a cat. J Am Vet Med Assoc 182:68-69.
Figure 5-51. Musca. Head of the adult fly.