SARCOPTES SCABEI 693 



are usually short but may be of considerable length ; they consist of two 

 segments, the distal one of which is serrated. The male genitalia are 

 very variable in structure, and are situated between the last pair of legs in 

 the middle line ; they consist of a pair of chitinous processes, behind and 

 on each side of which there are circular suckers. In the female there is 

 only one opening, the vulvo-anal slit, which is situated behind the second 

 pair of legs ; it becomes a large transverse slit in the fecundated female. 

 During copulation the sexes become attached to each other by their 

 posterior ends. Banks gives the following key to the more important 

 genera : 



BANKS' KEY TO THE GENERA OF SARCOPTINAE 



1. Anal opening on the dorsum ...,.,.., 2 

 Anal opening below ........... 3 



2. On small mammals, not bats ; third pair of legs in male without 



apical suckers t ....... Notoedres. 



On bats ; third legs in male with suckers .... Prosopodectes. 



3. Pedicel of suckers jointed ; mandibles styliform and serrate 



near tip ,.....,,.. Psoroptes. 

 Pedicel not jointed ; mandibles chelate ........ 4 



4. No suckers to legs of females ; parasitic on birds . , . Cnemidocoptes. 

 Suckers at least on legs I and II ; parasitic on mammals 5 



5. Legs very short ; in male the hind pairs equal in size ; body 



usually short t ........ Sarcoptes. 



Legs more slender ; in male the third pair is much larger than 



the fourth ; body more elongate ......... 6 



6. Female with suckers to fourth pair of legs .... Chorioptes. 

 Female without suckers to fourth legs ........ 7 



7. Hind part of male abdomen with two lobes .... Caparinia. 

 Hind part of male abdomen without lobes .... Otodectes. 



GENUS SARCOPTES, LATREILLE 



The species belonging to this genus may be recognized by the charac- 

 ters given in the above key ; some additional points are as follows : 

 The males have no suckers on the third pair of legs and are also devoid 

 of copulatory suckers ; in the female the first two pairs of legs have 

 suckers while the others are provided with hairs. The capitulum has 

 well-developed cheeks. The genus contains one species, Sarcoptes scabei, 

 de Geer, which is parasitic on man ; a number of varieties of it are 

 found on different animals. 



Sarcoptes scabei, de Geer. Body oval and marked by fine parallel 

 ridges which are interrupted on the dorsum by seven minute conical 

 spines, arranged in four regular rows. There are two longer spines on 

 the border of the epistoma and three shorter and stouter ones arranged 



