10 BULLETIN 766, U. S. DEPARTMENT OF AGRICULTURE. 
halfway down the posterior uterus, causing this organ to resemble 
a flat, more or less coiled ribbon, gradually enlarging toward the 
external organs of reproduction. As the developing larve are forced 
downward their axes gradually change until the axis of the posterior 
uterus and the larve isthe same. (Fig. 4.) 
At the distal termination of the posterior uterus is the “laying 
organ” or larvipositor. This is slightly chitinized and has a small 
tubelike opening just large enough for the passage of one larva. 
This organ, as well as the anus, arises in the venter of the sixth 
abdominal segment and is curved forward 
when at rest, fitting into the carinate 
venter of the fifth abdominal segment: 
The larvipositor fits into a curved chiti- 
nous hook or piercer, which is grooved, re- 
resembling a V in structure. Beneath this 
hook is a supporting organ arising from 
the fifth segment, which is strongly spined 
on both sides in such a manner that it 
reinforces the piercer while the female is 
in the act of attacking the host caterpil- 
lar. The parasite larve, as they are 
forced down the posterior uterus, are 
turned in some manner and are injected 
into the host, with the anterior end first. 
This was the conclusion the writer 
reached after making a number of dis- 
sections of females after they had de- 
posited part of their young. In these dis- 
sections some of the larvze were found to 
be inclosed in a very thin membranous 
Fic. 3.—Compsilura concinnata: 
Reproductive system of unier- 
tilized female. A, Ovary, 
showing ovarioles; B, paired 
oviducts; C, anterior uterus; 
D, accessory glands; F, sper- 
mathece ; F, posterior uterus; 
G, rectum, showing rectal 
papille; H, lateral lobes of 
dorsum of sixth abdominal 
segment; J, reinforcement of 
piercer, from dorsum of fifth 
abdominal segment ; J. piercer ; 
K, larvipositor. Greatly en- 
larged. (Original.) 
sheath, which fitted the body very closely, 
while others were found naked. This 
leads to the inference that Compsilura 
deposits both bare and inclosed larve. 
Pantel suggests that this might be possible on account of a prolon- 
gation of the egg stage, due to the absence of an appropriate host. 
DISCUSSION OF LARVA STAGE OF COMPSILURA CONCINNATA. 
Compsilura larve pass their entire life within the body of the host. 
The young larva is introduced generally into the intestines, where it 
is motile, floating free until just previous to molting into the second 
stage, when it becomes attached to one of the stigmata or vesicles of 
the branching trachea. This is done by means of the three anal hooks 
