APAITTELES MELANOSCELUS GIPSY-MOTH PARASITE. 21 



With this arrangement all of the light entering the chamber comes 

 from beneath, through the glass bottom of the chamber and through 

 the cloth-coverecl bottom of the tray. Five minutes after the cham- 

 ber is in this position practically all of the Apanteles have left the 

 top of the chamber and are found dispersed over the bottom of the 

 tray, where the gipsy-moth larvae are feeding and crawling. The 

 parasites begin ovipositing in the caterpillars immediately after 

 they have been attracted to the bottom of the tray. 



When the caterpillars have been exposed to Apanteles melano- 

 scelus for a sufficient period the operations are reversed; the cham- 

 ber is placed on a black-covered surface with the end of the cham- 

 ber opposite the end where the tray is to be removed, facing the sun. 

 Light is now admitted by removing the black paper over a space of 

 6 or 7 inches, as shown in Plate V, B at L. In a few minutes most 

 of the parasites will congregate in the top of the chamber at the 

 light end. The opposite end of the chamber can now be opened 

 without danger of any of the parasites escaping. The tray is with- 

 drawn slowly, care being taken that all of the Apanteles have left 

 it. If any still remain, they will fly to the light end of the chamber 

 when disturbed by touching them with a small camel's-hair brush. 



As soon as the tra}^ has been removed another one is introduced and 

 the process is repeated as long as the supply of Apanteles melanoscelus 

 lasts. The larvae parasitized in this manner are fed in the trays until 

 the parasite maggots issue. The resulting cocoons are removed each 

 day for colonization. 



A breeding chamber stocked with 300 adults of Apanteles melan- 

 oscelus^ with the sexes equally divided, can be used about one week. 

 Each tray should contain about 10,000 first-stage gipsy -moth larvse. 



The period of exposure of the larvae to the parasites varies with the 

 temperature and time of day. The parasites are most active during 

 the middle of the day. The larvae were enclosed in the chamber about 

 two hours during this part of the clay. Earlier in the morning and 

 later in the afternoon the larvae were exposed for about three hours. 

 An average of about 1,000 parasite cocoons were removed from each 

 tray. Undoubtedly many more than a thousand larvae were para- 

 sitized in each tray, but there is always a certain amount of unavoid- 

 able mortality of first-stage larvae in feeding trays. Many of the 

 larvae are weak and do not get to the food and many are injured when 

 the trays are cleaned and the larvae fed. 



SUCCESS OF COLONIES AND DISTRIBUTION OF A. MELANOSCELUS. 



Records of the success or establishment of colonies liberated and 

 of the distribution of the parasite are obtained by collecting host 

 material from the field and rearing the parasite from these larvae at 

 the laboratory, or by collecting the cocoons of the parasite in the 

 field. 



