20 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I23 



Peromyscopsylla hesperomys pacifica Holland, Canada Dept. Agr. Techn. 

 Bull. No. 70, p. 176, pi. 40, figs. 319-321, 324,a-e, map 41, 1949. 



Differs from other subspecies of hesperomys in details of P. and F. 

 in the male, the seventh sternum in the female, and the dorsal bristles 

 of the mesonotum, which are fine and erect, especially in the male. In 

 the male, the dorsal and ventral margins of the immovable process of 

 the clasper (fig. 17, F.) are almost parallel, not markedly divergent as 

 in h. hesperomys, the length of the lower being more than one-half 

 the upper (average length: lower, 95 microns; upper, 153 microns). 

 The characteristic bristle on the posterior margin of P. is usually more 

 than one-half the width of the movable finger, not less (average, 57 

 microns) ; F. (fig. 17) is about two times as high as long, or more 

 (average length, 138 microns ; width, 72 microns), triangular in shape, 

 with posterior angle about at midpoint, in absolute length somewhat 

 longer than h. adelpha, and definitely narrower than in h. ravalliensis. 

 Eighth sternum with narrowly rounded upper lobe, not as broad as in 

 h. hesperomys, bearing usually two long bristles and one short one ; 

 sinus between upper and lower lobes quite deep, not shallow as in 

 h. hesperomys. In the female, h. pacifica may be distinguished by the 

 fact that the upper lobe of the posterior margin of the seventh sternum 

 (fig. 24) is broader and more convex dorsally than in h. hesperomys, 

 and the sinus is much broader ; in cases where actual breakage of the 

 margin of the lower lobe has not occurred, this portion is evenly and 

 broadly convex. 



Peromyscopsylla hesperomys pacifica ranges from the west coast of 

 British Columbia, Washington, and Oregon, east to the Cascade and 

 Coastal Mountain ranges. 



Length. — Male, i. 95-2.1 mm.; female, 1.8-2.45 mm. 



Types. — Holotype, male, and allotype, female, Canadian National 

 Collection, Ottawa, from Peromyscus sp.. University of British Co- 

 lumbia campus, Vancouver, British Columbia, Canada. 



Records of Specimens Examined 



Canada. British Columbia (Microtus oregoni serpens, Peromyscus sp., P. 

 maniculatus, P. w. aiisterus, P. m. interdictus, P. m. oreas). 



United States. Oregon: Clackamas County (Peromyscus maniculatus 

 rubidus) ; Hood River County (P. m. gamheli) ; Linn County (P. m. rubidus) ; 

 Multnomah County (P. m. rubidus). Washington: Lewis County (P. 

 maniculatus) . 



Discussion of the Subspecies of P. hesperomys 



Peromyscopsylla hesperomys has long been regarded as a typical 

 parasite of eastern Peromyscus. Records of the occurrence of this 



