6 BULLETIiS^ 1028, U. S. DEPARTMEIS^T OF AGRICULTURE. 



OVIPOSITION. 



The act of oviposition takes about one second. The female may 

 -alight upon a gipsy-moth larva from flight or walk up to one. In 

 either case the ovipositor is inserted and withdrawn very quickly and 

 practically always an individual egg is deposited. Many larvse 

 have been dissected after apparent oviposition had been observed 

 and in no case has more than one egg been found from a single 

 oviposition and only rarely have dissections been made which failed 

 to show the presence of an egg. Often the larva attacked thrashes 

 about so violently that it and the parasite fall, but rarely does the 

 parasite fail in its object. After ovipositing in a larva the female 

 usually proceeds to another victim, but occasionally will oviposit a 

 second time before leaving the caterpillar. She apparently does not 

 examine a prospective host but attacks it whether it has previously 

 been parasitized or not. This practice of occasionally' placing an 

 egg in a parasitized caterpillar is unfortunate as only very excep- 

 tionally will more than one maggot develop within a single host. 

 The parasite favors the posterior half of the caterpillar for oviposi- 

 tion, but will oviposit in any segment of the body. 



The females of A. inelanoscelus which issue from hibernating 

 cocoons prefer to parasitize the first and second stage gipsy-moth 

 larvae but will oviposit successfully in third-stage larvae if they are 

 present. When the next or summer generation of adults appear, 

 most of the gipsy-moth larvae are in the third stage. This is the 

 stage most heavily attacked by this generation, although many 

 fourth-stage caterpillars are successfully parasitized, Apanteles 

 females of this generation often attempt oviposition in fifth and 

 sixth stage larvae but are not so successful, for they are hindered by 

 the long hairs of large larvae. 



There was considerable variation in the number of ovipositions 

 different individuals would make. Between 200 and 300 oviposi- 

 tions per female were often obtained in these experiments. The 

 greatest number of ovipositions secured by a single female of A. 

 melanoscelus was 535. She actually had gipsy-moth larvae before 

 her for 510 minutes, making these ovipositions a little faster than 

 one a minute.^° The parasite was allowed several oviposition periods 

 each day and she would parasitize the gipsy-moth larvae as fast as 

 they were introduced for from 30 to 60 minutes. The first day the 

 periods of oviposition were a little longer than during the follow- 

 ing days. This female issued Maj^ 23 from its hibernating cocoon, 

 but was not given an opportunity to oviposit until May 27, when 



^" This is about as fast as larvae can be introduced and witlidrawn by the process used. 

 Under more natural conditions, as found in tlie large breeding chamber, the females were 

 often observed to oviposit G or 7 times a minute. 



