30 ' STUDIES ON ACARI. 



long; the two spines on its dorsal surface are not very long, but 

 slender and rod-like, being almost straight in this sex, parallel, and 

 blunt at the end. 



d . Abdomen usually considerably shorter than cephalothorax+capi- 

 tulum. Other proportions of body much as in the female. Dorsal 

 spine of capitulum apparently more curved than in the female. Male 

 sexual orifice situated above and slightly in front of the transverse 

 groove between the first and second pairs of legs. Penis long, slender, 

 and usually curved; just before the end it has the appearance of being 

 narrowed to form a short neck, the end itself being shaped like the 

 flame of a candle. 



Author's measurements : — 



Female. Male. 



Total length of body (inch capit.) . . 200-232 /^ 190-204 /t 



Length of cephalotliorax+ capitulum . 126-131 /a 126 /x 



„ abdomen ....... 78-102 /^ 74-84 /i 



Greatest width of ceplialothorax . . . 65-70 ju. 62-08 /«. 



„ ,, abdomen .... 60-63 /j. .50-60 /«. 



,, „ capitulum (at base) . 46-5.5 /j. 44-47 /j. 



Length of capitulum 35-40 fx 34-37 /a 



„ dorsal spines on capitulum . 6 yx — 



„ penis — about 25 /a 



Host: The Horse (Equus cciballus). I have examined eleven females and three males 

 of this species from English horses (Leslie Linzell's collection). 



8. DEMODEX MUSCARDINI, Hirst, 1917. 

 D. muscardini, Hirst, Ann. Mag. Nat. Hist. (ser. 8) vol. xx. 1917, pp. 433-434. 



(Plate VI. figs. 27-29 ; Plate VII. figs. 31-33 ; 

 Plate VIU. figs. 35, 36.) 



2 . This JDemodex is a short form, and very like that of the house- 

 mouse, but the capitulum is wider as compared with its length and 

 armed with differently shaped spines. The general shape of the body 

 is also rather diff'erent in this species. Width of cephalothorax a little 

 more than four times up to four and a half times the total length of the 

 body (incl. capitulum). Cephalothorax-j-capitiilum a little less than 

 the length of the abdomen. Capitulum rather short, being wider than 

 long (at the base). Spines on dorsal surface of capitulum rather short, 

 curved, the end narrowed. Penultimate segment of palp salient and 

 pointed laterally, as in D. musculi. 



6 . Body a little less than four times up to a little more than b\ 



