DERMACENTOR VENUSTUS 361 



about five-eighths of an inch in length, belonging to the family 

 Argasidae. Like the other members of the family it has no 

 dorsal shield and has the margin of the body produced in such 

 a way as to conceal most of the head and legs. Unlike most 

 ticks the larvae are weak and do not feed 

 but transform to nymphs very soon after 

 the eggshell splits. The nymphs are 

 said to produce more painful wounds than 

 the adults and they can just as readily 

 transmit relapsing fever. 



An allied species, 0. savignyi, occurs 

 from Abyssinia through Arabia to India 

 and Ceylon and attacks man, camels and 

 horses. It is said to transmit the Indian ^ , ™ 



-,..., . Fig. 155. The tampan, 



form of relapsing fever in these countries, omithodorus moubata. x 3. 

 Like 0. moubata it attacks its host in its 



resting place, hiding in the daytime in dust or sand in or around the 

 squalid huts of the natives. Except in coastal towns, where it is 

 abundant everywhere, it is found chiefly in camps of long stand- 

 ing inhabited by men and animals. Burrowing to a depth of an 

 inch in dusty soil it can live without food for months. In Persia 

 0. tholosani is said to transmit African relapsing fever which has 

 been introduced there. 0. talaje of Mexico and Central America 

 has habits very similar to those of the tampan in Africa; it fre- 

 quently occurs in the adobe houses and attacks the occupants 

 at night. 0. turicata, the " carapato " of Central America, is 

 another very annoying species. Its bites are so severe that hogs 

 are said to have been killed in a single night by its attacks. 

 Though not proved it is very probable that one or both of these 

 species may be instrumental in transmitting the milder American 

 form of relapsing fever. It is almost certain also that another 

 tick, the " miana bug " of Persia, is capable of transmitting 

 European relapsing fever (see p. 364). 



Ticks and Spotted Fever. — The tick which is responsible for 

 the transmission of Rocky Mountain spotted fever (see p. 191) 

 is a wood tick, Dermacentor venustus (andersoni) (Fig. 156). This 

 is a handsome reddish brown species, the male of which has the 

 whole back marked with black and silvery-white lines, while 

 the female has only the small dorsal shield marked with silver, 

 the abdomen being deep reddish brown. This species is one 



