30 RESULTS FROM GIPSY MOTH PARASITE LABORATORY. 



EXPERIMENTS WITH FIRST-STAGE MAGGOTS ON LIVING AND 



DEAD MATERIAL. 



Some of these maggots were placed on mature active pupse, but in 

 every instance they showed little, if any, desire to bore through the 

 pupal cases. This would probably be an impossibility, as the exte- 

 rior of the pupae is tough and hard, but the maggots did not enter 

 even the soft prepupal larvae. In both cases the pupa? and prepupal 

 larvae were greatly disturbed and irritated when maggots were crawl- 

 ing on them, and thev wriggled violently, dislodging the maggots. If 

 they were placed on a soft, freshly formed pupa the maggots at once 

 would make frantic attempts to bite into it, but without success; 

 although, in one instance, when the membrane which holds the wing 

 cover to the body of the pupa became ruptured, the maggot took ad- 

 vantage of this opportunity of concealment and crawled beneath, 

 and although the maggot was still on the external surface of the 

 pupa it caused such an irritation by its movements that a dark secre- 

 tion oozed out, coming either from the pupa, maggot, or both, and in 

 the course of a few hours the wing cover became sealed to the body 

 of the pupa, so that only the anal stigmata of the maggot were left 

 exposed. After the lapse of about 12 hours the pupa was found to be 

 dead, and in 18 or 20 hours the maggot disappeared into the body of 

 the pupa. A dissection was made the following day. The maggot 

 was found dead midway in the body of the pupa. This would seem 

 to indicate that the environment which the maggot found within the 

 pupa was not favorable for its development. 



To further illustrate the above idea the writer took active pupae, 

 making a puncture about midway in the body of each, and allowed a 

 live maggot to crawl in, but in all cases the maggots died, showing 

 that they can not live under such circumstances. However, a few 

 came out of the pupae and died on the outside. Similar experiments 

 were made on dead material with entirely different results. In most 

 cases the maggots went in without experiencing any difficulty and 

 usually survived, which showed that they were in a natural en- 

 vironment. 



RELATION OF DECOMPOSITION TO OVIPOSITION. 



It was observed that the flies would not oviposit on freshly killed 

 material in the cages, even though the females had been ovipositing 

 previously on older decomposing caterpillars. This would seem to 

 refute the parasitic theory and would tend to show that the material 

 must reach a certain stage of decomposition before the females would 

 oviposit. Selecting the only cage where females were ovipositing 

 the writer removed all the old material and replaced it with a single 

 freshly killed caterpillar. The flies at once ceased to oviposit, 



