34 STUDIES ON ACAEI, 



DEMODEX ARVICOL^ var. MUSCULI, Oudemans, 1898. 



(Plate XI. figs. 38-40 ; Plate X. figs. 41, 42.) 



D.folliculorum var. musculi, Oudomans, Tijdschr, f. Ent. 1897, vol xl. p. 269. 

 D. musculi, Oudemans, Ent. Ber. Ned. Ver. 1909, vol. ii. no. 47, pp. 318 & 319. 

 I), musculi, Hirst, Ann. Mag. Nat. Hist. (ser. 8) vol. xx. 1917, pp. 233 & 234, 

 text-fig. 2, pi. ix. fig. 2. 



2 . The Demodex occurring in the Mouse is a minute species. The 

 proportions of the body vary considerably in female specimens, some 

 being rather short and wide, others more elongated and much more 

 slender; even the oephalothorax differs greatly in width (see figs. 39, 40). 

 Body from a little more than four up to about six times as long as the 

 width of the oephalothorax. Abdomen sometimes only a little longer 

 than oephalothorax + capitulum, but it may reach up to 1^ times as 

 long ; it is sometimes elongate sac-shaped, being widest some distance 

 before the rounded posterior end, but the sides may be practically 

 straight. 



6 . Body from a little more than 4 up to about 4J times the cephalo- 

 thoracic width. Abdomen a little longer than combined length of 

 oephalothorax and capitulum, its posterior end may be rounded off or 

 pointed. Capitulum usually wider than long (at base) ; distal end with 

 the outer angles strongly salient and pointed laterally; spines well 

 developed and sharply pointed as in the female. Male sexual orifice 

 situated above the epimera of the second legs. Penis shaped as figured ; 

 operculum of opening conical in shape. 



Beutonymph reaching a comparatively large size, its body up to 

 about 7 J times the width of the oephalothorax ; ventral tubercles, etc., 

 of the usual type. 



Author's measurements : — 



Female, Male. 



Total length of body (incl. capit.) . . 113-170 /x 126-154/* 



Leugth of ceplialothorax-h capitulum . 62-70 /x 67 u 



abdomen 90-104 /* 87 /x 



Greatest width of cephalothorax . . . 21-40 /* 30-34 /a 



„ „ abdomen .... — 30 /* 



„ „ capitulum (at base) . — 21 /* 



Length of capitulum — 17 /x 



„ spines on capitulum ... 6 /n — 



Length of deutonymph 235 a 



Its width 30 /x 



