P. A. Buxton 
133 
than the anterior pair; they consist of four joints not five; they terminate in 
extremely long stiff bristles. If one examines either the fourth or the fifth leg 
one finds that the first joint is oval in shape, and covered for two-thirds of its 
length in a portion of the general integument of the body which is shaped 
like a cuff; the joint is about 2J times as long as the remaining three joints 
put together. On the cuff which covers the base of the third leg there is a short 
ventral seta (Vi). There is no corresponding seta on the cuff which covers 
the base of the fourth leg, though a seta in this position has been frequently 
figured. The second, third and fourth joints of either leg are successively 
smaller and smaller. The second and third joints are without setae; the fourth 
joint bears two claws, and the extremely long terminal seta (HI) which 
corresponds to the ambulacrum of the anterior legs. This seta is equally long 
in the third and fourth pairs of legs. The terminal joint of the third pair of 
legs bears a minute seta (H 2) which is absent on the corresponding joint of 
the fourth pair of legs. (This seta is figured by Robin (1860) on both the 
third and fourth pairs of legs of Sarcoptes scabiei var. hominis.) 
I can find no trace of a fifth joint though Robin (1860), who is an unusually 
careful investigator, describes the five joints of the posterior legs in detail. I 
believe he was misled by the fact that the second joint has a double outline, 
due to a transverse band of chitin which strengthens the extremity. 
THE MALE. 
The length of the male is 205 to 230 microns, the breadth about 170, and 
the ratio of length to breadth 100 to 75 or 85. The dorsal surface (Fig. 13) 
resembles that of the adult female except in the following particulars. The 
seta D 1 is shorter and stiffer than in the female; the plastron (pi) is relatively 
wider, and much longer, so that its length slightly exceeds its breadth, and 
the shagreening is coarser at the posterior end than at the anterior; only 
about 7 to 9 scales on each side are present. There is a pair of posterior plas¬ 
trons (ppl) on the notogaster, between the dorsal and lateral rows of spines, 
and the shagreening of these is also relatively coarse. The shape of these can 
be seen from Fig. 13. There are only 12 spines ( sp ), arranged 3/3. The two 
pairs of anal setae (A 1 and 2) are present just as in the female: it must be 
due to an oversight that Munro (1919) figures one pair in his Fig. 3, two in 
his Fig. 6. The terminal seta II 1 of the third pair of legs is a conspicuous feature 
whether the mite is viewed from above or below, for it is as long as the body. 
The ambulacrum on the fourth leg is generally visible from above. There are 
three or four folds of integument on the side of the body on a level with the 
posterior plastron; they are very indefinite in number and degree of develop¬ 
ment. 
The ventral surface (Fig. 14) differs very greatly from that of the female. 
The posterior end of the sternum or fused first epimeres extends considerably 
further back than a line joining the extremities of the second epimeres; these 
extremities are frequently described as forked, but it would be more true to 
