PARASITES OF GIPSY-MOTH PUP^. 237 



If it is, in truth, single-brooded, like its host, it ought to multiply 

 much more rapidly than it has done, in view of the superlative 

 opportunities which the past 10 years have afforded. 



THE GENUS PIMPLA. 



The several forms of the genus Pimpla which have been reared 

 from gipsy-moth pupae received from Europe and Japan are not, 

 like the forms of Theronia, confusing and indefinitely separable, but 

 good and distinct species. There are 3 European, and a like number 

 of Japanese, making together, with the 2 American, a total of 8 of 

 the genus known to attack this host. Notwithstanding their variety, 

 all the species acting together in any one locality have never effected 

 the degree of parasitism resulting from the attack by Theronia in 

 the same locality. Being collectively of so little importance it is 

 unnecessary to say more concerning their relative importance indi- 

 vidually. 



Quite a little has been learned at first hand concerning the two 

 European species most frequently encountered, Pimpla instigator Fab. 

 and Pimpla examinator Fab. Both have been received in considerable 

 numbers in shipments of brown-tail moth pupae, and have been 

 liberated to the number of several hundred each in 1906, 1907, and 

 1909. Neither has since been recovered from the field. 



Both have been carried through all of their transformations in the 

 laboratory upon the gipsy moth, the brown-tail moth, or the white- 

 marked tussock moth, and in the case of P. instigator upon all three 

 above-mentioned hosts. The early stages of the larvae have not 

 been seen. In nearly every respect, so far as observed, they resemble 

 each other in habit and biology and also P. (Hoplectis) conquisitor 

 Say. and P. pedalis Cress., their American congenors. The one point 

 of difference between them is the tendency of Pimpla instigator to 

 hibernate within the pupa of the brown-tail moth. A very few have 

 been reared each spring since 1908 from cocoon masses received the 

 summer before. The proportion thus hibernated is very smaU. 



Pimpla instigator, like the American P. (Hoplectis) conquisitor, may 

 become hyperparasitic on occasion. On August 7, 1907, five female 

 specimens of P. instigator were confined with several tussock-moth 

 cocoons which contained the cocoons of Pimpla (Epiurus) inquisi- 

 toriella Dalla Torre, from some of which adults were emerging, and 

 all of which had been spun for several days. Oviposition was imme- 

 diately attempted. It was certainly successful, for on August 29, 

 at least two weeks after the Epiurus had ceased to issue, a greatly 

 dwarfed male P. instigator appeared and it was followed by another 

 similarly small male on September 3. There is not the slightest 

 doubt that the European parasite attacked the native and that its 

 larvae fed to maturity. At the same time it is not likely that it would 



