264 PROCEEDINGS OF THE NATIONAL MUSEUM vol. loi 



of accessory setae on ventral shield. Anal shield as in adults but lack- 

 ing accessory setae. Endopodal shields slenderer than in female. Ven- 

 tral body setae as in female. Metapodal shields more oval than in 

 adults. Peritreme not well developed. Epistome as in adults. Chelae, 

 maxillae, palpi, and legs as in female. 



Size. — In 15 measurable female specimens, body length varied from 

 925 IX to 1,225 /«; body with from 450 jx to 760 /a; mean length was 

 1,047/* ; mean width 657/x. Three male specimens measured 840/1, 850ju,, 

 and 875 /* in length ; body width in each of these specimens was 500 /t. 

 Three nymphs measured 800 /i in body length ; one of these measured 

 485 ju, in width ; another was 500 /a in width ; one specimen was 850/i in 

 length. 



This species differs from /. spiniger in many respects, of which the 

 following are outstanding : Female : Many of dorsal setae barbed ; su- 

 tures of presternal area with spines ; less than half as many accessory 

 sternal setae as spiniger; sternal shield rectangular with rounded cor- 

 ners ; genitoventral shield flask-shaped ; with over twice as many acces- 

 sory setae as spiniger ; anal shield with only two accessory setae ; both 

 chelae with teeth ; legs slenderer than in spiniger and lacking heavy 

 spur on coxa of leg I and coxa and femur of leg II ; tarsus I slender, 

 tapering gradually toward distal end; most setae of legs small and 

 slender. Male : Dorsal shield covers nearly entire dorsal surface ; ven- 

 tral shield expanded posterior to coxae IV; with only two pairs of 

 accessory setae anterior to coxae IV ; special setation of legs. Nymph : 

 Setation and chelae as in female ; only two pairs of accessory setae on 

 ventral shield. 



Distrihution and hosts. — This species has been taken from Arizona, 

 California, Colorado, and New Mexico on the following: Thomomys 

 hottae., Colorado Desert, Calif., February 17, 1934; Thomomys sp., 

 Lincoln County, N. Mex., July 16 and 19, 1947; Dipodomys merriami 

 merriami., Westmorland, Calif., July 21, 1933; Dipodomys deserti 

 deserti^ "Westmorland, Calif., July 21, 1933; DipodoTnys merriami 

 simiolus^ Dos Palmos, Calif., March 1934; Peromyscus maniculatus 

 ruflnus^ Mogollon Mountains, N. Mex., August 30, 1933 ; Peromyscus 

 sp., Monterey, Calif., December 30, 1948 (Bureau of Vector Control 

 collection, California Department of Public Health) ; Neotoma alhi- 

 gula., Santa Rita Mountains, Ariz., May 18, 1939; Perognathus sp., 

 Monterey, Calif., October 21, 1940; Perognathus calif ornicus., Mon- 

 terey, Calif., July 9, 1939 ; Perognathus inornatus, Kern County, Calif., 

 March 26, 1930; Perognathus xanthonotus, Kern County, Calif., April 

 19, 1930 ; Onychomys leucogaster arcticeps, Logan County, Colo., Sep- 

 tember 30, 1926 ; Citellus burrow, Davis, Calif., August 12, 1948 ; "spiny 

 pocket mouse," Pasadena, Calif., April 4, 1933 (Bureau of Vector Con- 

 trol collection, California Department of Public Health) . 



