262 INSECTS AFFECTING DOMESTIC ANIMALS. 
Ixodes ricinus Linn. 
A very common tick-upon the little ground squirrels in the Missis- 
Sippi Valley is a species which Dr. Marx 
has determined for me as ricinus. If 
this be identical with the European 
ricinus, its habits would seem to be some- 
what different, as there it is said to oc- 
cur on dogs and other large mammals, 
but here it is apparently confined pretty 
closely to small rodents. 
The figure will serve to distinguish it, 
and it is hoped that it may receive the 
attention of students, so that the full 
details of its habits may be _ better 
S known. 
Fie. 155.—Inodes ricinus—enlarged (orig- Ixodes reduvius, erinaceus, and margi- 
ae natus, Hyalomma egyptium and afri- 
canum, and Dermacentor reticulatus are among the species recorded as 
troublesome in the Old World. 
Family SARCOPTID 2. 
This family includes species which are strictly parasitic, and all may 
be considered as normally infesting the skin, those species which occur 
within the quills of feathers, in burrows of the skin, or in the subcuta- 
neous tissue, or on internal organs, being extreme forms and doubtless 
in all cases derivatives from species that first lived on the surface. 
In fact, the extreme forms of mites in this family show in a beautiful 
manner the gradual adaptation to different modes of living and lead to 
the worm-like condition presented by Demodex. 
The species are all minute, often almost invisible to the naked eye, 
the skin striated or furrowed, usually white or transparent, the mouth 
parts fitted for biting or suction, the tarsi generally with sucking disks 
for attachment, and the eyes wanting. 
THE PIGEON PLUME MITE. 
(Falciger rostratus Buchholz.) 
These mites live in the feathers of the pigeon and other birds, and 
some very interesting facts have been brought to light by the studies 
of Megnin and Trouessart, which show that the mite may undergo a 
peculiar transformation during the immature stages, whereby, instead 
of remaining on the feathers outside the body, they migrate within the 
skin and live in the subcutaneous tissue or attached to the blood ves- 
sels of the neck. In this form they are rather worm-like, and were 
originally described as a distinct species, Hypoderas columbe. 
