INSECT FAUNA OF HUMAN EXCREMENT 



579 



Marlatt, attracted to freshly dropped horse manure. January 

 20 and May 14, 1890, other specimens were reared from horse 

 manure, the last lot of manure being collected on November 

 27, 1889, so that the insect hibernates in either the larval or pupal 

 condition (probably the latter) in or just under old manure. 



This species has not been bred from human excrement, but 

 has been observed in out-of-door privies at Snickers Gap, Vir- 

 ginia, Alexandria, Virginia, and at Charlestown, West Vir- 

 ginia. 



Pseudofyrellia cornicina Fabr. 



The flies of this genus probably all resemble in their larval 

 habits those of the genus Pyrellta, the larvje of which live in 

 foul animal matter. The present species is a shining, metallic 

 fly. According to observa- 

 tions made by the writer in 

 1889, while studying the 

 horn fly of cattle, it seems to 

 be a very abundant feeder 

 upon cow dung. In many 

 fields in Virginia he found 

 that almost every cow drop- 

 ping of the previous day 

 (this was in July) contained 

 one or more clusters — one 

 hundred or more in a cluster 

 — of the elongated white 

 eggs of this species, almost 

 hidden from view, and evi- 

 dently deposited after the 

 dung had dried sufficiently 

 to become somewhat hard 

 on the top. The eggs had 

 then been thrust into a crack 

 and placed in little erect bunches near the surface. It was ascer- 

 tained that a generation in midsummer averages from ten to fif- 

 teen days. About fifteen pounds of these cow droppings was 

 brought to Washington and distributed in various standard breed- 

 ing cages, and the numbers in which the adult flies issued from 



Fig. 28. Pseudopyrellia cornicina : a, 

 egg mass iu situ — natural size; b, egg show- 

 iug method of hatching ; c, sculpturing of 

 egg ; d, sound egg ; e, full grown larva— all 

 except a enlarged (from Annual Report 

 U. S. Department of Agriculture, 1890). 



