DERMACENTOR 



717 



dorsum is speckled with brown punctations. The eleven festoons are some- 

 what quadrangular, each composed of a white area with one brown spot, and 

 speckled with brown punctations. Ventral surface with the first coxa biden- 

 tate, and the others with a single spine. Fourth coxa very large; about 

 twice as large as the third. Generative aperture on a level with the second 

 pair of legs. Stigma comma-shaped; hypostome with three rows of teeth on 

 each side. Palpi longer than hypostome. Size, 5 by 2-5 milHmetres. 



Young female: Oval depressed body, broader posteriorly than anteriorly; 

 reddish-brown in colour; about the same size as the male — 5 by 2*5 milli- 

 metres. Scutum very large, and marked like the anterior part of the male, 

 extending as far back as the third pair of legs, with eyes in the anterior 

 part of the lateral border. Dorsal surface of abdomen with a marginal 

 groove beginning behind the eyes, and three longitudinal grooves running 

 backwards, the two lateral beginning just behind the scutum, and the median 

 about the centre of the body. Posterior margin with eleven festoons. Ventraj 

 surface with fine hairs. Genital aperture at the level of the second coxa; 

 genital grooves close to- 

 gether at first, but diver- 

 ging laterally behind the 

 fourth coxa, and ending 

 between the second and 

 third external festoons. 

 Anus with short anomar- 

 ginal groove. Stigma 

 comma-shaped. 



Capitulum with the 

 posterior lateral angle 

 prolonged into a sharp 

 point. Porose areas cir- 

 cular. Internal apo- 

 physis of the mandible 

 with strong posterior 

 tooth ; external with 

 three successive teeth. 

 First coxa bidentate, 

 other three with spines. 

 Replete female ; Swollen 

 body laterally con- 

 stricted at the stigmata ; 

 of deep brown or slate 

 colour; size, 16 by 10 Fig. ^zj .—Dermacentov salmoni Stiles, 1909: 

 miUimetres. Male, Dorsal Aspect. 



Life-History. — The egg 

 hatches in seven to ten days, and produces a larva which feeds on some 

 animal for several days, and then, becoming swollen and of a uniform slate- 

 colour, drops off, and, becoming quiescent, moults and gives rise to the nymph. 

 This nymph again attacks an animal, and when fed drops off, and in ten 

 days moults and becomes the adult. The nymph, however, can hibernate. 

 If the adults do not obtain a host they die off quickly. 



Pathogenicity. — Nil. 



Dermacentor andersoni Stiles, 1905. 



Synonyms. — Dermacentor occidentalis of all writings on Rocky 

 Mountain spotted fever until some time after 1910; D. vemistus 

 Marx (in part only) ; D. andersoni Kieffer, 1907. 



Dermacentor with caudal margin nearly or quite semicircular. 

 Colour, greyish to red or deep red-brown. Eyes not prominent. 

 Scutum with whitish rust, and v/ith large or small punctations. 



