176 



PARASITES OF GIPSY AND BROWN-TAIL MOTHS. 



present has not been sufficiently large to make the rearing of the 

 parasite economically worth while. It is interesting and possibly 

 significant that there was no Schedius in the one locality where Anas- 

 tatus was sufficiently common to be considered as a parasite of con- 

 sequence, while in the other localities, where Anastatus was rare, 

 Schedius abounded. More than one instance has been observed in 

 which parasites having similar habits alternate but rarely or never 

 occur simultaneously in anything like equal abundance in one locality. 

 Two fairly consistent examples of this sort will receive further men- 

 tion later on, in which the tachinids Dexodes nigripes and Compsilura 

 concinnata, and TacJiina larvarum and Tricholyga grandis are respec- 

 tively involved. 



Schedius ktjvan.e How. 



Only one species of gipsy-moth egg parasite has been received at 

 the laboratory from Europe, but in Japan there are two, and, so far 



Fig. 17.— Schedius luvanse: Adult female. Greatly enlarged. (From Howard.) 



as may be determined from their comparative abundance in the 

 material from that country which has been studied, Schedius leuvanx 

 (fig. 17) is the more common and important as a factor in the control 

 of its host. It resembles Anastatus in its choice of host, and in the 

 fact that it is similarly limited through physical inability from attack- 

 ing more than a limited percentage of the eggs in each mass. In every 

 other respect the two species are widely different. 



Anastatus is a true egg parasite, and rarely attacks successfully 

 the eggs in which the young caterpillars have begun to form. She- 

 dius, on the contrary, is strictly speaking an internal parasite of the 

 unhatched caterpillar. Anastatus' passes through but one genera- 



