Siphonaptera 317 



gg. Antepygidial bristles five on each side; eyes absent; suture 



white. D. stylosus on rodents Dolichopsyllus Baker 



ff. Labial palpi four or five-segmented; asymmetrical (membranous 

 behind), apex acute. Hoplopsyllus anomalus found on Spermo- 



philes in Colorado Hoplopsyllid^ 



ee. Pronotum without ctenidium. Anomiopsyllus californicus and 



nudatus on rodents Anomiopsyllid^ 



cc. Very short fleas; flagellum of the antenna with pseudo-segments coales- 

 cent; thorax much shorter than the head and than the first tergite 



HECTOPSYLLIDiE 



Flagellum of the antenna with six coalescent pseudo-segments; maxilla 



blunt. The chigger on man (fig. 93). D . penetrans 



(=Rhynchoprion = Sarcopsylla) Dermatophilus Gu&in 



bb. Flagellum short, round, free portion of the first segment shaped like a 

 mandolin. 

 c. Thorax not shorter than the head, longer than the first tergite; flagellum 

 either with free segments or in part with the segments coalescent. 

 d. Head and pronotum with ctenidium; labial palpi asymmetrical. . . . 



ARCH^OPSYXLID.ffi; 



With four subfrontal, four genal, and one angular ctenidia. Widely 



distributed Ctenocephalus Kol. 



e. Head rounded in front (fig. 92a). Dog flea C . canis 



ee. Head long and flat (fig. 92b). Cat flea C . felis 



dd. Neither head nor pronotum with ctenidium. Labial palpi asym- 

 metrical, membranous behind PnLICID.ffi 



e. Mesostemite narrow, without internal rod-like thickening from the 



insertion of the cox^ upwards. Human flea, etc Pulex L. 



ee. Mesosternite broad with a rod-like internal thickening from the 

 insertion of the coxae upwards (fig. 89). X. (Lcemopsylla) cheopis, 



plague or rat flea Xenopsylla 



cc. Thorax much shorter than the head and than the first tergite. Echi- 

 dnophagidae. E. gallinacea, the hen flea also attacks man (fig. 96). 

 (=Argopsylla=Xestopsylla) Echidnophaga OUiff. 



