498 



THE ANIMAL PARASITES OF MAN 



when gorged they are lead-coloured, and may attain 12 mm. in 

 length by 6 to 7 mm. in breadth. 



The dog tick (fig. 360) lives in thickets on leaves, etc., and attacks sheep and 

 oxen, and more rarely dogs, horses, and human beings, into the skin of which the 

 female bores with the rostrum in order to suck blood ; the bite is not dangerous, and 

 sometimes is not even felt. Inflammation, however, is set up if the creatures are 

 forcibly removed from the wound, as the rostrum as a rule is torn off in the process. 

 If left alone or smeared over with some grease vaseline, oil, butter, etc. the 

 creatures drop off spontaneously. Sometimes the entire tick bores itself into the 

 skin ; they also appear to be permanent inmates of kennels. 



[The species /. reduvius is the same as /. ricinus, Latreille. 

 The male is 2*35 to 2'8o mm. long; the body is dark brown, almost 

 black, with a pale, almost white, margin ; there are also traces 

 of reddish mottling. Coxae of the first pair of legs with a short 

 spine. Rostrum much shorter than that of the female ; shield oval ; 

 anal shield small, about one-third the length of ventral shield. The 



adult female varies from 2*80 

 to 3*5 mm. when not distended, 

 but when gorged may reach 

 10 mm. long. The shield and 



FIG. 359. A., the rostrum of Ixodes 

 ricinus (male) ; B., the terminal joint of the 

 maxillary palpi of the female. Enlarged. 

 (After Pagenstecher.) 



FIG. 360. Female of Ixodes ricinus, 

 gorged full, dorsal and ventral surfaces. 

 2/1. (After Pagenstecher.) 



legs are dark blackish-brown, body deep orange-red with four dark 

 longitudinal lines, paler beneath and light grey in front. When dis- 

 tending it is pale red to grey or white ; when fully gorged olive-green, 

 or dark red to black, with irregular yellow streaks on the back and sides 

 just before egg-laying. Sexual orifice opposite fourth pair of legs. 

 The nymph varies from r6o to 1*70 mm. long when fasting; the 

 body is olive-white, opaque, with four distinct brown posterior 

 markings and similar anterior ones, leaving a pale centre to the 

 shield. When fully gorged it is 3 mm. long. As the nymph distends, 

 it changes from opaque white to blue-black, and finally black. The 

 little larva is o'8o to 1*50 mm. long, transparent with olive-green 

 intestinal markings ; as it becomes inflated it changes to blue-black, 

 and then black. There are no eyes. It is widely distributed, and 

 chiefly attacks sheep ; sometimes it occurs on dogs and also attacks 



