238 PARASITES OF GIPSY AND BROWN-TAIL MOTHS. 



have done so had the cocoons of the native not been associated with 

 the proper host of the other. 



The third species, Pimpla brassicarise Poda, is much less commonly 

 reared from either the gipsy moth or the brown-tail moth than the 

 other two. Apparently its habits are identical. 



Hardly enough have been received of the three Japanese species to 

 indicate their relative abundance. The most striking of them, 

 Pimpla pluto, appears to be the only one of the trio which has been 

 described, and to the others Mr. Viereck has given the names P. 

 disparis and P. porthetrise. It is possible that they are just a trifle 

 more common in connection with the gipsy moth in Japan than are 

 the corresponding species in either Europe or America. At the 

 same time Theronia has outnumbered all three together in the 

 Japanese material studied at the laboratory. 



Hardly anything is known about them. Not enough have been 

 received to make colonization possible, and only upon one occasion 

 to permit of laboratory reproduction with fertilized females, and upon 

 this occasion there was no time to devote to their further study. 



Presumably, except for minor differences, all of the Japanese 

 Pimpla will be found to conform very exactly in biology and habit 

 to the American and European. All will probably be found to 

 attack a very large variety of hosts, and all will defer their attack 

 until their host has entered the prepupal or pupal state. The 

 females of all will probably be ready to oviposit for a new generation 

 almost immediately following their emergence, and the length of life 

 cycle, dependent upon temperature, will be about three or four weeks. 

 There will necessarily be" more than one generation each year unless 

 the hibernating individuals should live long enough to deposit eggs 

 for another hibernating generation, as might easily be possible in the 

 case of Pimpla instigator, and conceivably possible in the case of 

 each of the others. 



Pimpla conquisitor and Pimpla pedalis are among the most 

 generally effective of the pupal parasites of the medium-sized cocoon- 

 spinning Lepidoptera in the Northeastern States. The first named 

 is perhaps the most common and effective of all the parasites of the 

 tent caterpillar and about as effective as any other one as a parasite 

 of the tussock moth. It does not vary much in relative abundance 

 from one year to the next, and appears to play a part which is rather 

 to be compared to that taken by the birds than to that taken by 

 most of the parasites. It is, like Theronia, so impartial in its atten- 

 tions to all of the different species of its hosts as scarcely to be 

 affected by an unusual abundance or unusual scarcity of any one 

 among them in particular. 



The same is very likely to be true of the European and Japanese 

 species. The part played by each in the localities where it is native 



