POO. PARASITES OF GIPSY AND BROWN-TAIL MOTHS. 
attack unparasitized caterpillars and its larve 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 Apanteles 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 
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