INSECT FAUNA OF HUMAN EXCREMENT 



569 



in a privy. Tlie species has not been captured in houses. It is 

 evidently a very rapid breeder, and Mr. Pratt's notes indicate that 

 between June i and June 7, 1899, an entire generation developed, 

 that is to say, from larvae deposited June i the first adult fly issued 

 early in the morning of June 7. It is only fair to say that the 

 weather was very warm, the average temperature being esti- 

 mated at 90° F. This fly is one of the first to be attracted in 

 the summer time to freshly deposited excreta and its larvae ap- 

 pear to be eagerly sought for by the Hymenopterous parasite 

 Alysia rudibunda Say. 



Another undescribed species of the genus Helicohia was cap- 

 tured upon excrement by Mr. Busck, in Porto Rico, in Febru- 

 ary, 1899. 



Family MUSCID^. 



This family is a rather unsatisfactory complex of forms, sys- 

 tematically speaking, and comprises many flies of such varying 

 habits that it is difficult to generalize concerning them. 



Mtisca domestica Linn. 

 The house fly was first studied by the writer in 1895. Its 

 breeding habits were specifically mentioned by Packard in 



Fig. 23. Musca domestica : puparium at left ; adult next, with enlarged an- 

 tenna ; larva and enlarged parts at right-enlarged (original). 



1873, and by Taschenberg in 1880. Early accounts by De 

 Geer (1752) showed that the larva lives in warm and humid 

 dung, but the duration of the different stages was not mentioned. 



