THE CHALCIDOID GENUS PEEILAMPUS. 43 



at this laboratory and briefly described by him in an earlier bulletin 

 of this bureau.* The maggots rarely leave their host until after it 

 has become full fed and prepared for pupation in the fall. The 

 tachinid maggots pupate soon after emerging from their hosts, the 

 pupae remain unchanged during the winter, and the subsequent 

 transformations are accompUshed quite early in the spring. 



In case the planidium chooses a maggot of Varichseta as its host, it 

 remains endoparasitic until the puparium is formed. During the 

 process of histolysis the Perilampus either orients itself in such a 

 manner that it will be external to the tachinid pupa when pupation 

 is completed, or it emerges from the pupa immediately after pupa- 

 tion; in either case, of course, it remains within the puparium. 

 When parasitic upon this host the planidium, so far at least as the 

 writer has been able to learn, normally hibernates in this stage and 

 probably without nourishment. 



It is quite likely, however, that a late warm fall would start the 

 development of the planidium on Varichseta at once. This would 

 without doubt result in the death of the secondary parasite, as it 

 would scarcely be able to pass the winter in the normal larval stage. 

 In fact dead second-stage Perilampus larvae have occasionally been 

 found upon the pupse during the winter, and this would seem to be 

 evidence in corroboration of the above statement. It is probably 

 an attempt to go through two generations per year, as this insect 

 does, without much doubt, farther south, and the individual speci- 

 mens found in the second stage during. the winter in New England 

 are probably those from the puparia which emerged as larvae from 

 the caterpillars earliest in the fall, although we have no absolute 

 evidence that this is the case. The development, or rather the con- 

 duct, of the planidium up to and including its change from endo- 

 parasitism to ectoparasitism, as stated on a previous page, seems 

 entirely dependent upon the development of its host, such are the 

 intimate relations between the two. After the planidium has 

 emerged from its host development takes place in the usual way. 



As A Parasite op Limneeium validum Cresson. 



Of the primary hymenopterous parasites attacked by Perilampus 

 probably the most common one is Limnerium validum Cresson, an 

 ophionine parasite emerging from the older caterpillars in the fall 

 and hibernating as larva in a silken cocoon. The larva of this para- 

 site, like that of Varichseta aldrichi, does not reach full maturity until 

 its host has prepared for ])upation, and the cocoons are to be found 

 in the same situations as the pupae of Hijphantria and are afforded 

 the same protection. In this respect it differs radically from the 

 other species of Limnerium parasitic upon the fall webworm. 



1 Technical Series, No. 12, Part VI, p. 103. 



