DEVELOPMENT OF A HYMENOPTEROUS PARASITE 527 
moving form, running about on the body of the parasitized 
Hyphantria larva seeking for a place to enter. Having accom- 
plished this, it attacks the larva of the parasite contained within. 
The planidium grows, becomes more robust, passes through a 
short resting period and after an ecdysis, emerges as the second 
stage larva. This differs greatly from the planidium, in its ovate 
shape and transparent integument, through which the tracheal 
system may be seen. The head is bent underneath the ante- 
rior portion of the body. Following an ecdysis, growth becomes 
rapid and the third larval stage is reached. The mouth parts 
are situated in a depression, beneath which are two bulb-like 
appendages, probably representing the maxillae. The antennae 
are represented by two large rounded elevations. The segments 
forming the head are somewhat constricted off from those that 
follow. Each of the first two thoracic segments bears a pair of 
medio-lateral tubercles and just above them another pair. Each 
of the three following segments has a larger pair of tubercles. 
The tracheal system is conspicuous at this stage. 
Timberlake (’12) has described the larval stages of the Ichneu- 
monid, Limnerium validum (Cress.), a parasite of the larva of 
Hyphantria cunea (Drury). The first stage larva has a heavily 
chitinized head and a long caudal appendage. ‘The latter the 
author considers to be respiratory in function. The oral aper- 
ture is surrounded by a chitinized rim within which there is a 
broader rim. On the posterior inner margin of the latter is a 
chitinized plate bearing two teeth, separated by a median angu- 
lar indentation. There is a pair of curved sharply pointed man- 
dibles. During the growth, the proportions of the head and 
caudal appendage change, the body becoming more elongate and 
the folds of the integument, at first so prominent, are later 
represented by mere creases. The second stage larva appears 
after the first moult and may be distinguished from the pre- 
ceding by the soft unarmored head, the slightly bilobed labium, 
the strong, curved mandibles and the large funnel-shaped mouth 
cavity. The caudal appendage is greatly reduced in size, but 
the larva itself is somewhat longer. than that of the first stage. 
The segments are very conspicuous at this time. The third 
