PARASITES OF GIPSY-MOTH CATERPILLARS. 



189 



Fig. 28.— Apanteles solitarius: Adult female and cocoon, 

 larged. (Original.) 



En- 



On the other hand, studies with the parasites of native insects 

 have revealed the existence of what may be called accidental or 

 incidental parasites. These may be important parasites of one 

 insect and of no importance whatever in connection with another, 

 nearly allied. Sometimes this is due to the fact that the one species 

 of host may excite in the mother parasite the desire to oviposit, which 

 is not excited by the other, and occasionally, as has more than once 

 been observed, the pres- 

 ence of the favored host 

 in the immediate vicinity 

 will induce the parasite 

 to oviposit in another 

 species which under 

 otherwise identical cir- 

 cumstances would be en- 

 tirely ignored. At other 

 times an insect may 

 be acceptable to the 

 mother parasite, but for 

 some reason unaccept- 

 able to her progeny, so that only a very few out of the many eggs 

 which are deposited will go through to maturity, and the species will 

 be of necessity considered as rare and unimportant. 



The fact that there are included in every list of the parasites of a 



given host a few species which are thus to be considered as incidental 



or accidental lends force to the contention that among the recorded 



parasites of the gipsy moth are several at least which come into the 



same category. Just which these are is not altogether plain at this 



time. 



Apanteles solitarius Ratz. 



Cocoons of a solitary species of Apanteles (fig. 28) which attacks 

 the very young to half-grown caterpillars of the gipsy moth through- 

 out the greater part if not the whole of Europe have occasionally been 

 received in shipments in which the caterpillars were not all in the last 

 or next to the last stage. In those shipments which consisted of cater- 

 pillars in the third, fourth, and fifth stages at the time of collection, 

 the cocoons of this species have been the most common. In no 

 instance has a sufficient number been received to make possible any- 

 thing like a satisfactory colony of this species, and in all scarcely more 

 than 100 have been received since the beginning of the work. 



The parasite undoubtedly attacks the first-stage caterpillars as 

 well as those of the later stages up to the fourth at least, and per- 

 haps the fifth. The host probably molts at least once, subsequent 

 to attack, and remains alive after the emergence of the parasite larva, 



