4 
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68 Psyche [June 
moult-skin to the newly moulted host. In cases where the 
Chrysopa larva died in the laboratory, the planidium invariably 
crawled out on the end of a hair, attached itself by the caudal 
sucker and awaited the approach of a new host. Apparently the 
planidium takes no nourishment until the Chrysopa larva spins its 
- cocoon and pupates, after which it begins to feed and develops in 
much the same way as the writer has described 
for P. hyalinus (loc. cit.), excepting that it is 
never an internal parasite so far as has been 
observed. 
It is difficult to understand just what is 
gained, from the standpoint of Perilampus 
infesting Chrysopa, by this extraordinary habit, 
since the Chrysopa larva is easily accessible to 
the normal method of oviposition and is in 
fact parasitized in the larval state by a number 
of parasites which oviposit directly into the 
host. In the case of Perilampus hyalinus, how- 
ever, and other species having similar habits, 
the advantage is obvious, since by no other 
method could access be had to the larve of the 
primary parasites. In the case, too, of those 
species of Perilampus infesting wood-boring 
Coleoptera and gall-making and stem-infesting 
Lepidoptera (the correctness of which records 
the writer is frank to confess he previously 
looked upon with doubt), the usefulness of this 
Fig. 4.—Planidium 
of Perilampus chry- 
method of oviposition taken with the active  sope var., greatly en- 
planidium stage is readily seen, since in this ea en 
way access is easily gained to the endophagous 
host through the wanderings of the planidium. Needless to say, 
this type of reproduction forms one of the most extraordinary 
adaptations to environment in the entire field of entomology. 
