266 PARASITES OF GIPSY AND BROWN-TAIL MOTHS. 



attack imparasitized caterpillars and its larvae develop as satisfac- 

 torily upon the one as upon the other, and at the expense of the 

 other internal parasites as well as of the primary host. But the 

 matter does not stop here. The adults issue from the hibernating 

 nests at just about the time when the Apan teles are issuing from the 

 young caterpillars and spinning their cocoons in the molting webs, 

 which are very frequently in the outer interstices of the very same 

 nests from which the Pteromalus are also issuing. The females of 

 the latter are ready to oviposit almost immediately following their 

 eclosion, and will oviposit with the greatest freedom in the cocoons 

 of Apanteles or of Meteorus whenever they chance to encounter 

 them. Thus it comes about that the Pteromalus, after passing one 

 generation as a primary parasite of the brown-tail moth, immediately 

 passes another as a secondary upon the same host. Undoubtedly it 

 would thrive equally as well upon Mesochorus as upon Apanteles. 

 Proof of this could unquestionably be secured through the careful 

 dissection of the very large number of cocoons from which it had 

 issued in the laboratory, some of which, it is certain, must have con- 

 tained Mesochorus as well, but proof is really unnecessary. By 

 doing so, it becomes tertiary upon the same host as that upon which 

 it is habitually and regularly a primary and secondary parasite. 



Entedon, were it to follow Pteromalus through its varied adventures, 

 would in like manner (as it probably does) become successively sec- 

 ondary, tertiary, and quaternary. 



Monodontomerus, commonly a primary parasite upon the pupa of 

 the brown-tail moth or gipsy moth and only present as a regular 

 guest in the winter nests, is none the less pretty intimately connected 

 with them in other ways. It directly attacks the cocoons of the 

 Apanteles, acting in all respects like a secondary parasite, and thereby 

 comes into direct conflict with Pteromalus, one of the other of which 

 must develop at the expense of its competitor. It also will become 

 tertiary whenever it chances to attack a cocoon containing Meso- 

 chorus as a secondary parasite on Apanteles. It is also a parasite of 

 tachinid puparia, and especially of tachinid puparia which it encoun- 

 ters associated with the gipsy moth, or the brown-tail moth, and 

 thereby becomes a parasite of Zygobothria and in consequence a 

 secondary parasite of the brown-tail moth. 



Should Apanteles and Meteorus, or Apanteles and Zygobothria 

 chance to become located in the same host, the Apanteles, because 

 of its more rapid development in the spring, would certainly be the 

 winner. 



When Meteorus and Zygobothria enter into competition for pos- 

 session of the same host individual, Meteorus is invariably the win- 

 ner and is in no way affected by the presence of the other parasite. 

 In fact, Zygobothria is twice apt to be the victim of Meteorus, which 



