10 
spiracles are very minute. There is no anal opening, but its position 
is indicated .by a short curved transverse impression just ventro- 
cephalad of the anal extremity. The mouth parts are so well shown at 
fig. le as to need no •description. The form and general appearance of 
the full-grown larva are also shown at fig. la-. 
On September these larva' were found to be spinning their cocoons. 
These cocoons, at first white and afterwards turning gradually to a pale 
yellow-brown, becoming much the same color as the cocoon of the 
Orgyia, are denser in structure and composed of a considerably finer 
quality of silk. They are long oval in shape, the longest reaching a 
length of HI mm. by 4 mm. in diameter. The cocoons spun by the 
larva* issuing from a single caterpillar are closely applied together and 
adhere so firmly that it takes some little force to separate them. They 
e a b 
Flo. 2. — Pimpla inquisitor: a, shrunken tussock moth caterpillar bearing parasite eggs in vita; 
b. egg; c. eggs in situ .■ '/. larvae, full grown, feeding on spun-up caterpillar; <\ cocoons of parasite 
within Orgyia cocoon — a, d,e slightly enlarged, c still more enlarged, b greatly enlarged (author's 
illustration, from Yearbook, Dipt. A.gric, 1805). 
are applied side by side and so closely that their oval outline becomes 
more or less angular at the points of application. The fastening 
together is not exactly regular, since one or more cocoons will frequently 
extend farther out than the others. Twenty-four hours after the 
spinning of the cocoon the larva' were still found unchanged, but at 
forty-eight hours, or on September 8, they changed to pupae. 
All of the adults issued together on September 14, leaving fifteen 
days as the duration of the life round, as follows: llgg, one day; larva 
before spinning cocoon, seven days; larva after spinning cocoon, one 
day; pupa, six days — total, fifteen days. 
This rapidity of development is somewhat surprising. The writer has 
recorded a much greater rapidity with certain Chalcidids, but is not 
familiar with any record of a similarly rapid development with an 
