THE HABITS OF CERTAIN SARCOPHAGIDiE. 31 



although they would crawl about over it. Two days later the writer 

 observed one of the female flies in this cage spending the most of 

 her time crawling about over this caterpillar. A little later she 

 began to make a buzzing noise with her wings and was feeling here 

 and there with her proboscis over the body of the decomposing cater- 

 pillar. Proceeding to the anterior portion of the caterpillar a few 

 segments back of the head she succeeded in puncturing the decaying 

 skin with her proboscis, and then moving along far enough so that 

 the end of her ovipositor was directly over this puncture she slowly 

 deposited a maggot which immediately, true to its instincts, worked 

 its way through this puncture into the body of the caterpillar. Sev- 

 eral maggots were deposited by this fly, and later a second female 

 was observed to oviposit on the caterpillar in the same incision. This 

 not only indicates that a certain stage of decomposition must be 

 reached, but that the skin of the caterpillar must be either broken, 

 or in such a condition that the female fly can puncture it with her 

 proboscis before she will oviposit, thus allowing an opportunity for 

 the maggots to crawl into the dead host. There were a few living 

 pupse in this cage, and although the females not infrequently crawled 

 about over them, they did not attempt oviposition. This was the 

 case with a freshly killed caterpillar which was placed beside a dead 

 specimen upon which flies were ovipositing, but when decomposition 

 reached the proper stage, the flies began to oviposit freely. It must 

 be stated here that the true source of the flies in the cage with which 

 this last experiment was tried was unknown, and that they were 

 selected only for the reason that they happened to be the only flies 

 available that were ovipositing. They were secured from a jar 

 containing dead European Calosoma beetles which had been exposed 

 for several weeks to the attack of various species of sarcophagids. 

 It is possible that these flies might have been imported from Europe, 

 but this is extremely doubtful. 



CONCLUSION. 



These experiments indicate very conclusively that the sarcophagids 

 in New England do not destroy living gipsy-moth larvae or pupae in 

 the field. From a collection of 2,666 specimens not a single sarco- 

 phagid was reared. 



In cages the flies would not oviposit on healthy or recently killed 

 caterpillars or pupae, but did so freely after they became slightly 

 decomposed. 



First-stage maggots, when placed artificially within living pupae, 

 failed to develop in every instance, showing that the conditions were 

 not favorable for their growth. 



