186 



PARASITES OP GIPSY AND BROWN-TAIL MOTHS. 



The reproduction of the parasite in the field as a result of these 

 early attempts at colonization was far in excess of expectations. 

 The rate of reproduction in the laboratory (as indicated in the table) 

 was greatly exceeded in the open, and hundreds of thousands of eggs 

 in the immediate vicinity of the colony sites were known to be 

 parasitized when the coming of cold weather put a stop to insect 

 activity. In the one colony which was most closely watched, the 

 parasitized eggs averaged some 30 to the mass (fig. 27), while every- 

 where within 50 yards of the center egg masses were so thick in spots 



as to hide the bark on the trees. 

 Beyond the distance mentioned the 

 number per mass fell off very rapidly, 

 but some were found several hundred 

 yards away from the point of libera- 

 tion, in striking contrast to the re- 

 sults following the colonization of 

 Anastatus. 



In October adults of what ap- 

 peared to be the second generation 

 were not uncommon in the field, and 

 on any warm day they could be 

 found, apparently ovipositing for a 

 third generation. At the same time 

 larvse and pupae were in abundance, 

 and only a few days' exposure to the 

 warmth of the laboratory was needed 

 to bring them out from eggs collected 

 in the field. Collections of eggs were 

 made from time to time during the 

 fall, in order that assurance might 

 thus be had of the continued well- 

 being of the parasite, and until De- 

 cember nothing untoward occurred. 

 The first real winter weather came 

 at the end of that month, and a few 

 days later a lot of eggs was col- 

 lected and brought in. Not a sin- 

 gle parasite issued. The experiment was repeated and with the 

 same results, and although many hundreds of- masses have since been 

 collected (some of them in the spring, after the caterpillars had 

 issued for the purpose of determining whether there might not be 

 reproduction of hibernated adults at that time, and the rest of them 

 in the fall to see if by any chance the parasite had escaped detection 

 in the spring), no trace of its existence could be found. In every 





I 1 



■ x 1 



1 I 

 ■ 



Fig. 27 —Gipsy-moth egg mass, showing exit holes 

 of Schedius kuvanx. Enlarged about four times. 

 (Original.) 



