356 INSECTS INFESTING DOMESTIC ANIMALS. 



" First — Dennatodectes ovis; sheep itch-mite of Gerlach, b}' 

 whom it was considered as peculiar to sheep ; but the most 

 recent authority restores the name Psorojytes equi, horse itch- 

 mite of Gervais, considering the species infesting the horse, 

 cattle and sheep as identical. It is distinguished from the 

 itch-mite of man (Sarcojjtes scabei. — Latr.) by two or three 

 important characters. The four anterior legs and two of the 

 hind ones, at least in the males of each species, are furnished 

 with sucking disks placed on comparatively long pedicels or 

 stems. In the itch-mite of man, as far as I can ascertain, 

 these pedicels are only one-jointed. But the most important 

 difference is that the mouth of the human itcli-mite is fur- 

 nished with scissor-like jaws or iii|)pcrs with which they can 

 readily cut into the skin and form their subcutaneous burrows. 

 The sheep mite is furnished with comparatively slender lan- 

 cet-like mandibles, to the sides of which the little palpi or 

 mouth feelers are glued, thus forming a sort of tube, one part 

 of which is capable of piercing. But Avhile this peculiar form 

 of the oral apparatus enables them to pierce and suck, it 

 deprives them of the power of cutting, and hence, notwith- 

 standing the general opinion to the contrary, they arc not 

 subcutaneous in their habits and do not form true burrows, 

 as the human itch-mite. It lays its egg on the surface of the 

 skin, to which they adhere by a gluey matter. The length of 

 time these require to hatch in such situations is not positively 

 known, but some placed in a bottle and kept to the warmth 

 of the body hatched in fourteen days. The young, which are 

 produced from these have only six legs, but after several 

 changes of skin or moultings they acquire eight, which is the 

 normal iniiu1)or of this class. Witli the little sucking disks of 

 their feet they are enabled to cling firmly to the skin of the 

 sheep. By piercing the skin with their laucct-like mandibles, 

 irritation and a sjieeies of inflannnation of the skin follows 

 and an exudation takes i)hK'e which uUimatoly forms 

 the seal). As stated by a writer on this subject : ' Examina- 

 tion will disclose spots on the skin white and hard, the 

 center marked with yellow points of exudation wliich ad- 

 heres to the wool, matting the fibres t(\i:ctlier. Tlu' wool 

 may be firm on these spots and no scales are seen in this 



