THE PEDICULI. 409 
structural details. Then the parasite is born closely resembling 
its parents. 
There are two great divisions of the Anoplura ; in one, the true 
lice, the insects have suckers ; and in the other, the bird lice, there 
are jaws. The Pediculi which are parasitic upon the hair and 
clothes of man are, of course, disgusting on account of their asso- 
ciation with dirt and disease, but nevertheless they are interesting 
creatures to the naturalist, on account of their wingless and 
degraded condition, as well as from their not undergoing meta- 
morphosis. Moreover, there is much interest accompanying their 
birth, for the females preponderate, and they can lay fertile eggs 
time after time without the help of the male, and generations of 
Philoptcrus selcifrons. 
Pediculus capitis. 
females succeed each other and produce fertile eggs under the 
same exceptional circumstances. 
The Head Louse, drawn above, is not very unlike a long bed- 
bug ( Cimex ) in its early stage. 
The lice without suckers, and with jaws that can bite through 
the skin, afflict most domestic mammals and all sorts of birds. In 
tracing their development within the egg it becomes evident that 
some of the earlier characters of the embryo are retained per- 
sistently ; thus the permanently enlarged forehead of the bird louse 
can be recognised during very early egg life, but this structure 
disappears very soon in the embryos of the true lice with suckers. 
The legs and claws of the different species of Philopterous or 
bird lice vary much in structure, on account of the peculiar con- 
ditions in which the parasites are placed and live. One genus, 
which has a species parasitic on the porpoise — the only marine 
