446 ABACHNIDA 



Key to the genera of Ixodidae here described: 



Oi Pedipalps much hunger than broad. 



\ Eyes absent 1- Ixodes 



&2 Eyes present 2. Amblyomma 



02 Pedipalps very short and thick. 



61 Stigmal plate round 3. Margaropus 



6, Stigmal plate comma-shaped 4. Dermacentoe 



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 nnn. 

 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 

 ' .• ^0f=5555==5:5j^ the female is a 



fe^^^^-1^ strong median 

 '♦■W'SM spine: cosmopoli- 

 • i\;i7 Cv^*'^'^) ^^^^^' often common 



3 \^ ^^ on domestic ani- 



/^ X ^ ^ mals, rabbits, etc., 



Fig. 700 — Anihlyomma americanum (Hooker). A, dorsal ^1^0 on man. 

 aspect of female; B, the scutum; C, stigmal plate. 1, -r oPOTknlaria 



first leg; 2, pedipalps ; 3, rostrum. ■*■• !>i'«*'l' Ui«*Ai» 



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 {BoopMlus 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. hovis 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. 



