130 EEPOET 108, U. S. DEPARTMEXT OF AGRICULTURE. 



There are only a few genera; the better known ones may be tabulated as follows: 



1. Anal opening on the dorsum J 



Anal opening below 3 



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



suckers Xotocdrcs. 



On bats; third legs in male ^vith suckers Prosopodccfcs. 



3. Pedicel of suckers jointed; mandibles st^diform 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. ASarcopi^s. 

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



body more elongate 6 



6. Female with suckers to fourth pah" 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. 



Fig. 268. — Psoroptes communis var. 

 ovis: Male. (Author's illustration.) 



Fig. 2Q0.— Psoroptes communis var. avis: 

 Female and caroncle enlarged. (Au- 

 thor's illustration.) 



Sarcoptcs includes the species parasitic on man, although some other genera may 

 sometimes attack him. The human species is 5. scabci De Geer (figs. 2(54, 2G5). This 

 pest was formerly more common than now, particularly in armies. The intolerable 

 itching caused by the presence of these mites leads to wild and incessiint scratching, 

 which only serves to spread the infection and increase the inflammation. Cleanliness 

 is the best preventive. The best remedy is the use of an ointment containing suljihur. 

 If the affected parts are freely bathed in hot water and soapsuds the scaly portions of 

 the skin will be removed, and then the ointment can be applied with a certainty of 

 reaching the mites. The application should be repeated two or three times, each a 



