TWO SPECIES OF PARASITIC MITES. 335 
it, but in copulation it is turned backwards, when, of course, the 
episternum is also turned back beneath it. 
The external sexual organ of the adult female is simply a narrow 
slit running across the under surface of the body, about half way 
between the insertions of the second and third pairs of legs. It is 
rather an interesting fact, however, that the male does not copulate 
with the fully developed female, but with the female in what has 
been called the nymph stage, when the ventral opening into the 
oviduct has not yet appeared; another ecdysis being necessary 
before the adult form is assumed. I have not had the opportunity 
of observing the mode of copulation, but there would appear to be 
no doubt that the anus serves for the opening both of the intestine 
and the vagina. Fiirstenberg, in his comprehensive treatise on 
“ Die Kriitzmilben,” does not mention the opening in the middle of 
the ventral surface, but in Sarcoptes scabiei figured the oviduct as 
opening into a cloaea along with the intestine, evidently not 
recognizing the fact that the oviduct and vagina opened at different 
parts of the body. He also states that he saw a male and female in 
copulation, and that the penis was inserted into the anal opening. 
In the closely allied family of the “ Dermaleichidae” also, the 
arrangement of the female sexual organs is essentially as follows :— 
There is a post-anal opening leading by a duct into the Receptaculum 
seminis, which opens into the oviduct, at one end of which the 
ovaries are placed, and the oviduct opens on the middle of the 
ventral surface. It appears very probable that an arrangement of 
the parts similar to the above exists in the genus Sarcoptes. 
With the exception of the absence of a ventral sexual opening, 
and the slightly more posterior position of the anus, the nymph is 
very similar to the adult female. 
The larva is somewhat smaller than the nymph, and is only 
provided with six legs, the hinder pair of which end in long bristles 
as in the adult females. 
The egg is small, oval or somewhat ovate, and about half the 
length of the adult female. 
We have adopted Fiirstenberg’s name minor for this species 
instead of cati, which had previously been given to it by Héring, as 
the first is characteristic of the species itself (it being very small), 
and not merely of its habitat, for though it was first found on the 
cat, it has since been found on the rabbit and other animals, On 
