12 BULLETIN 766, U. S. DEPARTMENT OF AGRICULTURE. 
The larve differ somewhat in appearance in the three stages. In 
the first-stage larve the mouth-hook is single pointed, being heavily 
chitinized throughout with the exception of the inside areas of the 
divided posterior part. This posterior end is membranous and serves 
Fie. 5.—Compsilura 
concinnata: First- 
stage larva, right lat- 
eral view. Greatly 
enlarged. (Original.) 
as a place of attachment to hold the hook in posi- 
tion, this being true of all three stages. The 
first segment has a row of heavy spines around 
its base, while the second segment is thickly 
studded with the same kind of spines. The 
ventral part of the remaining segments is also 
fitted with the same spiny structure, in this case 
the spines extending upward laterally along the 
anterior border of each segment. All of the seg- 
ments are more or less covered with what, under 
the high-power microscepe, appear to be very 
small granulations. On the last abdominal seg- 
ment there is a peculiar set of hooks that make 
possible the determination of first-stage Comp- 
silura. These are for the purpose of attach- 
ment to the stigma of the host. (Fig. 5.) 
The second-stage larva of Compsilura differs 
from the first in three main points: (1) The 
mouth-hook is double throughout, the halves 
being jointed by a chitinous structure, and is 
jointed in one place (fig. 6) ; (2) the chitinous part of the hook extends 
farther basally, the whole outline of the hcok being more uneven; and 
(3) the heavy spines on the integument are lost in this stage, while the 
a oi 
iol) nated sala haan 
anterior border of each ab- 
dominal segment has twe 
or three rows of lighter 
spines, which extend com- 
pletely around the body. 
The first segment 1s more 
contracted on the ventral 
surface, grading off at a 
gradual angle to its junc- 
tion with the second seg- 
ment. The anal hooks 
are wanting in this stage 
and the permanent struc- 
ture of the anal stigmata 
is clearly shown. 
The third and last stage of the larva differs slightly from the 
second in the structure of the mouth-hook and spines on the body. 
The mouth-hook is still divided into two parts, but there are two 
joints in it. (Fig. 7.). The heavy chitinous structure does not ex- 
Fic. 6.—Compsilura concinnata: Anterior end of 
second-stage larva, left lateral view. Greatly 
enlarged. (Original.) 
