42 
THE WHITE SWAN LOUSE. 
(Ornithobius cygni Denny ; Ornithobius bucephalus Giebel.) 
This large and handsome species was quite certainly recognized by 
Redi and figured by him and has received frequent mention since. It 
iS a conspicuous species and appears to occur in 
great abundance on different species of swans, so 
that it is readily obtained. It has been recorded 
as occurring on the domestic and wild swan of the 
old world as well as the musicus and Bewickii, and 
= we have taken it in great abundance from the 
common swan of this country, probably the 
\ Trumpeter Swan. 
y The body in this species is whitish, but so trans- 
parent that all the internal organs are easily seen 
through the body walls. There are black points 
at the outer hind margins of about four of the 
abdominal segments, aS Shown in the figure, and 
the last segment is dusky or nearly black. It is 
4 millimetres iong (one-sixth of an inch) and 
the body rather slender and decidedly flattened. 
Altogether this species seems to be almost as 
FiG. 30.—Ornithodius cygni, beautiful and as graceful in its movements as the 
(Original.) bird which harbors it. Some of the specimens 
we have secured appear to contain blood, and while these parasites 
are not supposed to extract blood from their hosts it is possible that 
they may at times burrow deep enough to secure access to the capil- 
laries or feed upon blood that may have exuded from wounds upon the 
surface of the body of the bird. 
THE LOUSE OF THE CAT. 
( Trichodectes subrostratus Nitzsch.) 
While it is possible that this parasite was referred to by Ctto Fabri- 
cius about the year 1780 under the name of Pediculus canis, the first 
certain reference to it appears to have been the description 
by Nitzsch in 1818. Since that time it has been referred 
to by nearly all writers on the common parasites of ani- 
mals, but so far as we know there has been no special 
description of the different stages, and we must assume 74 
that there is no important departure from the habits of T~@ 
species that are more thoroughly known. f 
It is a little more than a millimetre in Jength and has ae 
much the appearance of the species occurring on other do- yy, 31 _7ri- 
mestic animals, but is distinguished particularly by the form chedectes subro- 
of the head, which is quite pointed, and the under part of the ress Sea 
