106 



PARASITES OF THE DOMESTIC ANIMALS 



or late stages, (lie diagnosis of sareoptie mange ma}' he iiia.de positi\'e 

 by the recovery of the Sareoptes. This shoultl he looked for as soon as 

 the presence of mange is suspected, as it is important to know with what 

 form of the disease we have to deal. The nymphie and puhescent males 

 and females live upon the body surface and among the crusts over all 

 affected parts. Immediately after they become impregnated the oviger- 

 ous females Ijurrow galleries beneath the epidermis in which they deposit 

 their eggs and live for a time with the young larvie (Fig. 05) . In man the 

 course of the galleries is marked by fine red hues from 8 to 15 mm. or 

 more in length, liut hi the horse these cannot he seen owing to the 

 thickness and jiigmentation of the ejiidermis. Th(> sarcopt is usually 

 lodged at the extreme end of the channel in the course of which her eggs 



Fig. G6. — Cult.s afffctoci with ad\'aiK-f'<.l .sareoptic mange (from author's photograph). 



are distributed. It has been estimated that approximately fifteen izi- 

 dividuals will be produced hi each of these sul:)epiderniic burrows, and 

 that about fifteen days are required, under average conditions, for their 

 full development and the appearance of the next succeeding generation. 

 The larva; issuing from the eggs live in the gallery for some time before 

 finally making their exit along its course, while the parent female soon 

 dies after ovulation is completed. Copulation takes place upon the 

 skin beneath the crusts, the males dying after the performance of this 

 function. As the males are also relatively less in luunber, it is the fe- 

 males which are more often met with. 



To secure the parasite for examination the crusts should be removeil 

 and skin scrapings taken in such a manner as to include a portion of 

 serous exudate with the epidermic scales. The material should be taken 

 from a part showing evidences of recent attack, the mites being more 

 likely to be found there than in the older lesions. This material, to- 



