THE FLEAS FOUND ON DOMESTIC RATS AND MICE. 97 



12. Genus Ctenophthalmus, Kolen. 



The species are numerous. The eye is vestigial; the head bears a comb, 

 and about midway between the palpi and the antennal groove there is a 

 distinct frontal tubercle situated in a groove. Two species are recorded 

 from rats. 



1. Ct. agyrtes, Heller. The genal comb consists of three teeth and the 

 pronotal one of sixteen. The non-movable process of the clasper of the male 

 (fig. 25) is separated by a sinus into a conical upper lobe and a shorter and 

 broader lower lobe, the latter being sinuate; the movable process is conical. 

 In the female the sternite of the seventh abdominal segment (fig. 22) is 

 produced into a broad rounded lobe, beneath which there is a narrow second 

 lobe.— This is a European species, common in England on field-mice and 

 bank-voles, and occurring also on Mus norwegicus when captured in the 

 open. 



2. Ct. assimilis, Tasch. The genal comb consists of three teeth and the 

 pronotal one of eighteen. In the S the non-movable process of the clasper 

 (fig. 24) is short and broad and bears a number of long bristles ; the movable 

 l)rocess has the shape of a boot held with the sole upwards. The sternite 

 of the seventh abdominal segment of the female (tig. 21) is produced into a 

 broad rounded lobe, beneath which the edge of the segment is twice slightly 

 incurved. — The species is found in Central Europe on field-mice ; it is 

 common in Germany on Arvicola arvalisy and has also been recorded from 

 rats ; it is apparently not found in England. 



13. Genus Ctenopsylla, Kolen. 



The species are easily recognised by the shape of the head (fig. 2d)) and 

 the comb-like arrangements of the bristles at the hind edge of the tibiae. 

 One of the species has been obtained from rats. 



1. Ct. musculi, Dugcs. Two of the bristles near the front angle of the 

 head are spine-like. — A widely distributed species, very common on rats and 

 mice, especially Mas musculus, with which it has spread. 



14. Genus Hystrichopsylla, Tasch. 



The few known species are all large and very hairy fleas, which are at 

 once recognised by the abdomen bearing one or more combs and the eye 

 being absent or vestigial. One species has been found on rats. 



