DEOSOPHILID^. 35 



vations, about their diameter apart, each with tliree radiated slits, 

 and a button, incomplete on inner side. 



From onions, in Pennsylvania. It is probably this snecies or its 

 close ally, T. incurva Loew. 



SEPSIDiE. 



The larvae of the Sepsidne are of the muscid shape; the fusiform 

 areas are not prominent except on the venter; the anal tubercle is 

 rather inconspicuous; the spiracles are situated on projections at 

 the tip of the body, and also in the pupae. Each spiracle has three 

 straight slits. 



They breed mostly in manures, but sometimes in decayino; fruit; 

 one species, the cheese skipper, has long been known because of its 

 occurrence on old cheeses. 



PiopMla casei L. 

 (Plate VII, figs. 122-124.) 



The body is of the usual shape, tapering in front. The head is 

 emargmate from above, each corner projecting in a papilla; there are 

 two well-separated great hooks. The anterior spiracles are rather 

 prominent and divided into about ten lobes. The sixth and follow- 

 ing segments have on the ventral base a narrow, transverse, fusiform 

 area in which the ridges are broken into minute teeth. The last seg- 

 ment has at tip two processes, each about three times as long as 

 broad at base, and rather more than their length apart; this last 

 segment also has a prominent outer angle each side near the base. 

 The posterior spiracles are situated on the inner tip of a slight pro- 

 tuberance, and each has three straight slits. Each main tracheal 

 tube is black for a short distance from the tip. 



The cheese skipper not only occurs in cheese, but also in hams, 

 especially the fatty parts, and in oleomargarine; there are several 

 records of its occurrence in people, and we have one such case. 



Alessandrini has recently made exj^eriments with this species on 

 dogs and finds that it passes through unmjured, while it may cause 

 intestinal lesions in the dog. He also found that the larva was 

 remarkably resistant to many chemical substances, supposedly destruc- 

 tive to life. 



DROSOPHILID^. 



Drosophila. 



(Plate VIII, figs. 133, 135-137.) 



Body rather slender in front; head with distinct papillae, two well- 

 separated great hooks; anterior spiracles obscure, not much ex- 

 truded, with eight to ten long branches or lobes; each segment of 



