SARCOPTES SCABIEI 



519 



camel, horse, ferret, lion, wolf, sheep, pig, etc., and two species 

 parasites of man (scab lei and scabiei-crnstoscc). There is no doubt 

 that they are distinct species. F. V. T.] 



The S. scabiei of man (S. scabiei var. hominis) (length of male 

 o'2 to 0*3 mm., and breadth 0-145 to 0*190 mm. ; length of female 

 c*33 to o ! 45 mm., and breadth 0*25 to 0^35 mm.) lives in the tunnels 

 that it excavates in the epidermis, and attacks by preference places 

 with thin skin, such as between the fingers, in the bend of the 

 elbows and knees, in the inguinal region, on the penis, on the 

 mammae, but may also affect other parts. The tunnels, which 

 vary from a few millimetres to a centimetre and more long, do not 

 run straight, but are somewhat 

 tortuous ; the female is found 

 at the terminal end. The tun- 

 nels contain the excrement and 

 oval eggs (0-14 mm. in length) 

 of the parasite ; the males are 

 rarely met with, as they die oft 

 after copulation ; the females 

 die after depositing their eggs. 

 The six-legged larvae hatch 

 out after four to eight days, 

 and after about a fortnight, 

 during which time they change 

 their skins three times and 

 undergo metamorphosis, they 

 begin themselves to burrow. 

 Transmission from person to 

 person rarely is effected 

 through linen, but by direct 

 contact (as in coitus) ; trans- 

 mission can be artificially 

 effected on horses, dogs and 

 monkeys, but not on cats. 



The smaller S. scabiei-cnis- 

 toscc, Fiirstenberg, is the cause of the itch that occurs chiefly in 

 Norway ; it is not certain whether this is a distinct species of 

 itch mite. 



[This is quite a distinct species, which is recorded from Germany and 

 France. Megnin (Parasitology, 1880, p. 165) described this as 5. scabiei 

 var. lupi. The female is 140 //, long, 340 /u, broad ; the male is 170 yu, long 

 by 150/4 broad. In Science (March 3, 1893, p. 125) is recorded that 

 at the Indiana Academy of Science Dr. Robert Hessler referred to 

 " a case of that extremely rare and almost extinct form of itch 



FIG. 368. Sarcoptes scabiei : male, ventral aspect. 

 200/1. (After Ftirstenberg.) 



