THE FLEAS OF NORTH AMERICA 105 



1914, in a lengthy paper reports some exhaustive studies on the bio- 

 nomics of this and a few other species. He found that cold (40° F.) 

 was fatal to the eggs of cheap is. that conditions of drought did not 

 affect egg production, but that low temperatures either checked or 

 prevented oviposition. Bacot found that the larvae of cheopis were 

 able to live from several days to over a month without food and that 

 the time consumed by the active larval period ranged from 12 to 84 

 days. The duration of the cocoon period was found to range from 7 to 

 1S2 davs. Adults kept in a box and fed on their natural host lived for 

 100 days. 



The oriental rat flea is the chief agent in the transmission of bu- 

 bonic plague, a disease that formerly took a frightful toll of life in 

 the Old TTorld. According to TTaterston (90) over seven million 

 deaths resulted from this disease in India between 1S96 and 1911. 

 This flea also is implicated in the transmission of certain types of 

 endemic typhus. 



Two species, XenopsyV.a brasiHensis and X. a-stia. as well as some 

 others, are frequently confused with X. cheopis. As pointed out by 

 Rothschild (65. p. 84) in 1914. brasiliensis differs from the other two 

 by having the antepygidial bristle situated on "a long pedestal" in the 

 male sex: while astia differs from brasiliensis and cheopis b}~ having, 

 in the male, a somewhat curved and ribbonlike posterior process or 

 lobe of the ninth sternal plate instead of a club-shaped one. 



Wagner (80, p. 3-5), in his catalog, indicates four synonyms of this 

 species. 



The Genus Hoplopsyllus Baker 



(Fig. 12, C) 



HoptosyUu* Baker, 1905. U. S. Natl. Mos. Proc. 29: 128. Type, Pulex anomalus 



Baker (by original designation). 



Anterior margin of front rounded. Genal comb absent. Frontal tubercle ab- 

 sent. Eves well developed, subcircular, black. Labial palpus 4-segmented, an- 

 terior margin thickened and well sclerotized, posterior margin weak, but slightly 

 sclerotized. Antennal club capitate or strongly clavate. Episternum III di- 

 vided into upper and lower parts by a deep horizontal suture. Pronotal comb 

 present, compo-sed of more than 8 black, apically acute spines, and not extend- 

 ing ventrally on either side to lower margin of pronotum. Hind coxa with a 

 row or patch of spinelets on inner surface. Segment V of each tarsus with 4 

 pairs of lateral plantar bristles. Abdomen without apical spines. 



Hoplopsyllus is confined entirely to the Northern Hemisphere, and 

 largely to the Xearctic Region. Two subgenera are recognized. 



The Subgenus HOPLOPSYLLUS Baker 



Antennal club capitate, segments anchylosed anteriorly. Antennal groove 

 closed posteriorly in both sexes. Clasper of male with a rather small but 

 broad anterior process, but without posterior fingerlike process ; movable finger 

 broad, crescentic. 



Certain kinds of squirrels are natural hosts. 



The type species of the genus Hoplopsyllus Baker has been recog- 

 nized, since its description, as a species apart from its congeners. For 

 this reason the genus was recently divided into two subgenera. The 

 chief differences between these two subgenera lie in the male genital 

 armature. 



