INSECT FAUNA OK HUMAN EXCREMENT 589 



male lays about 30 eggs and the duration of a generation in this 

 country is frequently as short as 18 days. In Germany the 

 average duration of a generation is four to five weeks and 

 there are two and three generations during the summer, the 

 larva? over-wintering in the puparium. The species is of cos- 

 mopolitan distribution. 



In the course of the present investigation this species was 

 captured upon human excrement at Travilah, Maryland. 



This species is shown in its different stages on Plate xxx, 

 at fig. 2. 



Family DROSOPHILID^. 



The minute flies of this family, commonly known as fruit 

 flies or pomace flies, are attracted to decaying vegetation, es- 

 pecially fruit, and are frequently found in houses in the autumn 

 about dishes containing pears, peaches and grapes. They are 

 attracted to fruit both for food and as places of oviposition since 

 their larvse live in decaying vegetable matter. 



D7'oso^hila ampelophila Loew. 

 This little pomace fly is the commonest species all over the 

 United States and occurs also in the West Indies. It is also re- 

 ported by Loew from South Europe. It does considerable 

 damage to canned fruits and pickles, breeds in decaying apples 

 and the refuse of cider mills and fermenting vats of grape 

 pomace. It is a rather rapid breeder and a generation may be 

 developed in 20 da3^s or less. In the present series of observa- 

 tions it was captured upon human excrement at Charlestown, 

 West Virginia, by Mr. Busck, and September 5, 1899, was 

 reared from miscellaneous deposits collected at Washington, 

 District of Columbia, August 31, so that it is a true excrement 

 breeder. As this fly is as has just been stated in the remarks 

 on the family Drosophilidae frequently found in houses in the 

 autumn about dishes containing fruit and as it also affects 

 canned fruits, pickles, raspberry vinegar and similar sub- 

 stances, this discovery that it will and does breed in human ex- 

 crement makes this species and the following very dangerous 

 ones. 



Proc. Wash. Acad. Sci., December 1900. 



