336 Capitulum of Psoroptes 
one of the chelicerae is nearly always more extended than the other, but they 
are equal in length. The palps (p) arise antero-laterally from the basis capituli, 
flanking the chelicerae. The base of each palp is excavated (Fig. 2 B) on the 
ventral surface so as almost to surround the origin of seta 1, which springs 
not from the palp but from the basis capituli. The dorsal surface of the palp 
is somewhat more heavily chitinized than the rest of the organ, and from it 
arises a short seta (s 3) directed forwards and upwards. The extremity of the 
palp is armed with about five delicate finger-like processes (/), covered with 
extremely thin, soft chi tin. In some dead specimens these are seen lying side 
by side (fig. 2 A), in others they are spread out from the ventral face of the 
extremity of the palp (fig. 2 B). 
I have made no observations on the manner in which these organs are 
used by the living mite, and it is difficult to see how such observations could 
be made, for not only are the chelicerae extremely small and colourless, but 
also the mite carries its head tucked down between the bases of the first pair 
of legs. It may be assumed that the mite obtains a secure hold on the skin 
of the host by aid of its ambulacra and tarsal claws, and that it then steadies 
itself by applying the finger-like processes closely to the skin. It would then 
bring the chelicerae into action, probably using setae 1 and 2 as organs of 
touch. 
Mr S. Hirst of the British Museum (Natural History) has been good 
enough to examine some of the material on which I have worked, and says 
that “they seem to be Psoroptes equi but are not very typical. It is probable 
that nearly all the forms of Psoroptes occurring on domestic animals are merely 
races or varieties of a single species." 
REFERENCE. 
Megnin, P. (no date). Les Acariens Parasites. Paris: Masson & Cie. 
