THE GENUS DEMODEX. 37 



12. DEMODEX RATTI, Hahn. 

 (Plate XT. figs. 46, 47.) 



$ . This species is long and slender, being about seven and a half 

 to eight and a half times as long as the width of the cephalothorax. 

 Capitulum narrow, being longer than wide. Cephalothorax also 

 characteristically narrow and much shorter than the abdomen ; the 

 latter is wider, but fairly long and vermiform. The two spines on the 

 dorsal surface of the capitulum are well developed, being longer than in 

 D. arvicoiw, they are pointed at the end. 



Author's measurements : — 



Female. 



Total length of body (incl. capit.) 237 /t 



Length of cephalothorax+capitulum 95/* 



„ abdomen — 



Greatest width of cephalothorax ...... 27-30 /x 



„ „ abdomen 36-38 /x 



„ ,, capitulum (at base) .... 21 /«. 



Length of capitulum 26 ft. 



„ spines of capitulum .... about 6 /a 



Host : I have examined three adult female specimens collected by Leslie Linzoll from 

 a Brown Eat (Battm norvegiciis). Mr. Linzell informs me that the parasites were very 

 abundant in the skin of this rat. 



13. DEMODEX SORICINUS, Hirst, 1918. 

 I), soricinus, Hirst, Ann. Mag. Nat. Hist. (ser. 9) ii. 1918, p. 145. 



(Plate XI. fig. 48.) 

 9 . A small species, the cephalothorax being fairly wide. Body a 

 little more than three times the width of the cephalothorax. Abdomen 

 pointed posteriorly and somewhat longer than cephalothorax -j- capitulum. 

 Capitulum wider than long. (The spines on the capitulum canuot l)e 

 seen in the unique specimen, which lies ventral side uppermost.) 



Female. 



Total length of body (incl. capit.) ...,.• 119 /a 



Length of cephalothorax + capitulum 49 fx. 



„ abdomen 70 /a 



Greatest width of cephalothorax 34-35 /a 



„ „ abdomen 26 /* 



,, „ capitulum (at base) .... 23 /x 



Length of capitulum 16 /* 



Host : Common Shrew {Sorex araneus castanens). 



The following Demodex was described as a new species but is almost 

 certainly the same as I), soricinus. 



