15 
The total number of specimens of the Pimpla reared appears to us to 
be very extraordinary, and in itself almost accounts for the nearly 
total annihilation of the first 1896 brood of tussock-moth caterpillars. 
The specimens of the Pimpla issuing in March and April, 1896, and 
of these there were 252, undoubtedly passed the winter in the Orgyia 
cocoons and mainly in the larval stage. They were plainly smaller on 
the average than specimens reared in the following midsummer and the 
previous September. No observations were made during the winter of 
1895-96 which would determine the actual condition in which the insect 
passes the winter, this statement depending upon observations made 
during the middle of December, 1896. On December 10, 1896, several 
cocoons of the Orgyia were opened and in some of them a number of 
specimens of this larva were discovered, in one instance as many as 
six. All were approximately of equal size and were apparently little 
more than half grown as compared with full-grown larve taken in 
late August and early September. They were, however, much con- 
tracted. Instead of being fusiform in shape, as are the full-grown 
summer larvie, they were broad oval, the broadest portion a little behind 
the middle of the body. At the same time, however, their greatest 
diameter did not exceed that of the late summer fusiform larvee. In 
spite of the smaller size, however, these larvie must be full grown, since 
each was inclosed in its characteristic cocoon. One of these larvie is 
shown at fig. 1), and its size line should be compared with that of fig. 
la, which represents a September larva. The small size of the hiber- 
nating larva is remarkable and is unquestionably almost entirely due 
to contraction, as is evidenced by the shortness of the body segments 
and by the somewhat serrated margin and by the fact that both the 
head and anal end are well drawn in. In color these hibernating larvie 
areesof a brighter and lighter yellow than those taken in late summer, 
and it can plainly be seen that there is a greater quantity of adipose 
tissue. It is worthy of remark that in the Orgyia cocoon containing 
six cocoons and hibernating larvie of the Pimpla there was also a single 
adult male of the Pimpla. It is doubtful that this individual was the 
offspring of a prior oviposition, and it was probably simply a rapidly 
developing individual from the same batch of eggs. Exact observa- 
tions have not been made upon this point, but it is likely that, as is the 
case with rapidly developing and externally feeding larve of Enuplectrus, 
as Shown by Schwarz, the removal of an individual larva far in advance 
of tle others results in the death of the remainder, probably through 
the admission of air to the wound and the consequent severe inflamma- 
tion of the host. 
Observations upon the method of hibernation of Ichneumonids are 
sufficiently rare to render this observation on the hibernating larvie of 
some positive value.! 
'Forstmeister Tischbein, in Entomologische Nachrichten, 1871, pages 155-160, shows 
that with the genera Ichneumon, Amblyteles, Dicielotus, Aithecerus, Herpostomus, 
Heterischus, and Phieogenes, the females (presumably fertilized) hibernate as a rule 
as adults, the males dying in auturan. He did not determine by microscopic exami- 
nation whether these overwintering females were fertilized. 
