SPECIES OF HAEMAPHYSALIS 627 



throughout the year, are most numerous during the months of April 

 and May, when the weather "is warm; with 'very rare exceptions it is 

 only the adult stage which attacks man. Towards 



the end of summer the adults leave the plants on which Bionomics and Life 

 .... . Processes of Derma- 



the}- rest when waiting lor a passing host, and crawl center 



under the grass and leaves to hibernate; the larvae 

 hibernate in the same manner. Bishop and King believe the mountain 

 goat to be the reservoir of the parasite of Rocky Mountain Fever ; 

 infected ticks, chiefly larvae and nymphs, occur on the ground squirrel 

 and the woodchuck, and these may carry the ticks from the higher 

 altitudes to the valleys where cattle usually graze. In man the adults 

 often fix themselves under the hair below the occipital region. In the 

 Bitter Root Valley the life cycle of the tick extends over two to three 

 years under natural conditions ; the adults do not become replete with 

 blood during the season in which they change to that stage. 



Dermacentor andersoni, like most of the other species of the genus, 

 requires three hosts in order to complete its life history ; variabilis, the 

 common dog tick in America, behaves in the same way. Dermacentor 

 nitcns, the American horse tick, and D. nigrolineatus and D. albipictus, 

 do not leave their hosts until they become adults, the females dropping 

 off when replete with blood. 



GENUS HAEMAPHYSALIS, KOCH, C. L. 



Eyes absent. Capitnliun short with a rectangular base. Palpi short, 

 the second segment generally humped externally. Body longer than broad. 

 Scutum brown without spots. Spiracles circular or in the form of a short 

 comma. Eleven festoons present, at least in the male ; anal groove with 

 limbs joining the genital grooves anteriorly. Coxa I has one spur and 

 coxa IV of the male is a little longer than the others ; trochanter usually 

 with a retrograde spur at its distal extremity. (Neumann) 



Neumann gives the following key for the determination of the species. 



NEUMANN'S KEY TO THE SPECIES OF HAEMAPHYSALIS 

 . . . . MALES 



1. .Second segment of palp without hump or with a hump on its 



. external side and towards its posterior border ... , . . . 2 

 Second segment of palp pointed externally at its posterior 



border ^ . _ . . . . . ( . t . . . . . , g 



2. Third segment of palp not recurved inwards 3 



