48 Genus Ornithodoros 



This species closely resembles 0. savignyi, from which, however, it may 

 easily be distinguished by the absence of eyes, and the details of its leg 

 structure {compare Figs. 70-73). The humps on theprotarsus of leg I are 

 sub-equal and toothlike, while the tarsus of leg IV is shorter and thicker 

 than in 0. savignyi, and its humps are nearly equidistant, the intervals 

 {proximal and distal) between them being as 4 — 5 1 . Less hairy than 

 0. savignyi 1 . 



Adults usually measure 8x6 or 7 mm. (Christy, 1903, p. 187 ; 

 Pocock, 1907, p. 195, and others), but the females, especially when 

 gorged, may attain I. 11 mm. (Donitz, 1906 ; Wellman, 1906), or 

 even 12 x 10 mm. when fully grown and filled with eggs and blood 

 (Button and Todd) 2 . The colour varies from dusty brown to greenish 

 brown in living specimens with occasional dull ochreus patches ; after 

 gorging it appears darker and turns reddish or blackish brown in 

 alcohol. Reference to the figures (Figs. 66-69) will give a better idea 

 of the appearance of the tick than a lengthy description. From the 

 observations of Newstead, Dutton and Todd, and of Donitz (1906, 

 p. 146 ; 1907, pp. 11, 20) and R. Koch, whom he cites, there appears to be 

 no doubt but that adults (8 — 9 mm. I.) may moult. Donitz states he 

 has observed females moult after ovipositing. Newstead, Dutton and 

 Todd (1907) raised a female from the egg and kept her under 

 observation for 25 months during which time she moulted six times. 

 Other specimens moulted 6 — 9 times during a year. Under favourable 

 conditions they may moult 2 — 3 times in two months. Mollers (1907, 

 p. 278) states that the nymphs moult after each feed of blood and that 

 they feed 6 — 7 times before reaching the adult stage, after which only 

 the males continue to moult. The females lay batches of eggs after 

 each feed but do not continue to moult. (This is contrary to what 

 Donitz states.) It is obvious, therefore, that there are several nymphal 

 stages, the number not having been clearly established. The largest 

 nymphs may equal adults in size, and we have noted that they show 

 a punctiform mark where the sexual orifice is situated in the adult, 



1 A point established by Donitz, 1906. According to Newstead (1905, p. 1696) the 

 species can be further distinguished by the dorsal process of the digit being bidentate in 

 0. moubata, but this is not of practical importance^ 



2 According to Mollers (1907, p. 278) ticks descended from the same parents may differ 

 considerably in size. The males are usually smaller than the females but the size is very 

 variable in both sexes. Nymphs of the same age which have fed 4 to 5 times may measure 

 3 — 4 or 8 — 9 mm. long. (This variability in size, also noticeable in other Ixodoidea, doubt- 

 less depends upon the amount of blood consumed.) 



