12 American Midland Naturalist Monograph No. 1 



grade into each other, the great majority of the species can be assigned generi- 

 cally with little or no difficulty. 



We accept as of good standing the following genera: 



1. Argas Latreille, 1795 3. Otobius Banks. 1912 



2. Ornithodoros Koch, 1844 4. Anlricola Cooley and Kohls, 1942 



Key to the Genera 



1 . With a definite sutural line separating dorsal and ventral surfaces (see fig. 4, G) 



Argas 



Lacking a definite sutural line separating dorsal and ventral surfaces 2 



2. Nymphs with integument beset with spines, hypostome well developed; adults with 



integument granular, hypostome vestigial (see fig. 6, C) Oiobius 



Integument of adults and nymphs essentially alike, mammillated or tuberculated, 

 and lacking spines; hypostome of various forms in nymphs and adults but not 

 vestigial 3 



3. Hypostome broad at the base and scoop-like (see fig. 53, B) (Associated with 



bats.) Antricola 



Hypostome of various forms but never scoop-like (Associated with various classes 

 of animals and including bats.) Ornithodoros 



