FLIES FOUND IN HOUSES 2$ 



Hermes (1911), who very carefully observed these flies, and 

 made numerous experiments with them, came to the conclusion 

 that they are more strongly attracted to light than many of the 

 allied species, and hence if by chance one of these flies finds its 

 way into the house, it soon escapes through an open window. 



Flies of this family are very commonly found about dead 

 animals, especially stale fish, excreta and other decomposing 

 substances. 



The e£gs are "cylindrical, rounded at both ends and slightly curved, smooth and 

 white."' Hermes states that they are deposited in irregular masses on the softer portions 

 of decaying fish, etc., e.g. around the eyes, around the anus and nostrils, and on 

 abrasions, and on the under sides of carcases. " This is due to the presence of much 

 liquid food at these particular portions, which the adults suck up while depositing the 

 eggs." The eggs are also laid on excreta and decaying matter of all kinds. Hewitt 

 (1910, p. 361) says: "The chief breeding place on which I have found it in this 

 country is on the backs of sheep. It is one of the destructive species of ' maggots ' of 

 sheep." 



Larva hatch in from 8 — 18 hours. When the eggs have been laid on carcases 

 "the young larvae at once eat into the softer parts, attacking the viscera, and later 

 consuming the muscular portions." For example an exposed "fish is eaten clean to 

 skin and bone, the skin remaining as a mere shell ; this too would be eaten to the 

 scales were the entire surface sufficiently moist. This is evident because the portion 

 of skin nearest the earth, where it is moist, is invariably eaten away, leaving a hole on 

 the under side, which incidentally allows a concealed means of escape during migration." 

 The actual feeding period varies, according to Hermes (p. 54), from two to two and 

 a half days and over. When full fed the larvae measure 10 — 11 mm. and very closely 

 resemble those of C. erytiirocephala in size and general appearance. 



Hermes, studying the larvae living under natural conditions on dead fish cast up on 

 the shore, states that before pupating the larviu migrate from the carcase on which 

 they have been feeding. 



" Migrating wholly depends on the food supply. If the fish is large enough, and 

 the number of larvae is not too great, migration takes place in from one and a half 

 to three days, during which time the larvae have reached their full growth. If the 

 number of larvae is large in proportion to the fish, migration takes place earlier. " 



"On leaving the remains, the larvae immediately burrow into the sand below or 

 close to the fish. The great majority burrow just beneath, going down two to six 

 inches into the sand and remaining there temporarily. This migration may take 

 place at any time during the day or night, though the tactics vaiy for these periods. 

 Burrowing temporarily just beneath the fish carcase during the day not only affords 

 protection from the intense heat of the sun, but also from birds. On cloudy days when 

 migration sometimes takes place away from the fish, the sandpipers, in numbers, feed 



on the plump migrating larvie During the night, or when the sand is cooled, 



migration from beneath the remains takes place, and it is then that the larvre travel . 

 a greater distance — fifteen, twenty feet or over — and then again burrow. Larvae that 

 were kept indoors in boxes were observed to repeat this performance several nights 

 in succession, each time burrowing for the day. The sand in the laboratory was not 

 heated by the sun, yet the larvae followed the normal habit and were characteristically 

 active at night." 



