446 ARACHNIDA 



Key to the genera of Ixodidae here described: 



a : Pedipalps much longer than broad. 



6j Eyes absent 1. IXODES 



6 2 Eyes present 2. AMBLYOMMA 



a 2 Pedipalps very short and thick. 



&! Stigmal plate round 3. MARGAROPUS 



& 2 Stigmal plate comma-shaped 4. DERMACENTOB 



1. IXODES Latreille. Eyes absent; pedipalps and beak long and of 

 the same length ; anal groove surrounds anus anteriorly and is open pos- 

 teriorly : over 50 species, about 14 in America. 



1. ricinus (L.). The castor bean tick. Body oval, in male 3.5 mm. 

 long and 2 mm. broad and high ; in female 4 mm. to 11 mm. long, accord- 

 ing to the amount of blood it has sucked, and brown or yellow in color ; 



at the base of the 

 first pair of legs in 

 the female is a 

 strong median 

 spine: cosmopoli- 

 tan; often common 

 on domestic ani- 

 mals, rabbits, etc., 



Fig. 700 Amllyomma americanum (Hooker). A, dorsal a l so on man. 

 aspect of female; B, the scutum; C, stigmal plate. 1, T _, _ _ 



first leg; 2, pedipalps ; 3, rostrum. SCapUlailS 



Say. Body 3 to 6 



mm. long and 2 mm. broad, with a dark brown shield: common in the 

 southern states on all kinds of wild animals, dogs, and cattle. 



2. AMBLYOMMA Koch. Eyes present; anal groove surrounds anus 

 posteriorly and is open anteriorly; pedipalps and beak long: 86 species, 

 4 American. 



A. americanum (L.). Lone star tick (Fig. 700). Body 4 mm. long, 

 3 mm. wide; the gravid female may measure 12 mm. in length and 8 

 mm. breadth; color of male brown, of female bluish, with a brown 

 scutum, the hinder end of which has a conspicuous yellowish spot, 

 which gives the animal its popular name: often common on cattle, also 

 on man. 



3. MARGAROPUS Karsch (Boophilus Curtice). Eyes present, often 

 indistinct; pedipalps short and broad, with the second and third joints 

 extended laterally into sharp points; spiracles round: 2 species, 1 

 American. 



M. annulatus* (Say) (M. bovis Riley). Texas cattle tick (Fig. 701). 

 Body oval and 2.30 mm. long, and brown in color in male, and elliptical 



* See "Texas Fever," etc., by J. R. Mohler. Bull. 78, Bur. Animal Industry, 

 Dept. Ag. 1905. 



