206 
HERBERT OSBORN. 
occasional one escape the scalding trough and succeed in 
finding another host. Of the vast number of hogs shipped 
to market and slaughtered at the great packing houses, none 
can bequeath the insects they have nurtured to their follow¬ 
ers. The amount of injury and the consequent need of pre¬ 
cautionary measures are, therefore, much less for this species 
than for many others. 
This is one of the largest species of the family, full grown 
individuals measuring a fourth of an inch or more in length. 
It is of a gray color, with the margins of the head and thorax 
and most of the abdomen dark; the head is quite long, the 
sides nearly parallel, with strong eminences just back of the 
antennae, which are set on the sides of the head, midway from 
rostrum to occiput; the legs are lighter, with dark bands at 
the joints; the spiracles are inclosed by a black chitinous 
eminence, and there is a broad black band on the last seg¬ 
ment, broken near the middle. (See Fig. 6.) 
The male has the abdomen marked beneath with a large 
black area extending forward from the end of the terminal 
segment, so as to occupy the central portion of the last three, 
segments. 
There is a curious provision in the feet for strengthening 
the hold upon the hair, which does not seem to have been 
hitherto described. 
It consists of a circular pad-like organ or disc in the outer 
portion of the tibia which is received in a conical cavity in 
the end of the tibia, and which can be forced out so as to 
press upon the hair held between the claws of the tarsus and 
the end of the tibia. 
Ordinarily, and always in the dead specimens, this is with¬ 
drawn so as to appear simply as a part of the end of the tibia,' 
and the spines located on its margin appeay to belong to the 
tibial rim, but if examined with sufficient magnification when 
the louse is alive it is easy to observe the extrusion of the 
organ. 
Whether similar organs exist in related species is yet un¬ 
determined, but it seems quite probable that they should, 
since in the specimens examined microscopically we have 
