174 
Larvae of Fleas 
pairs of hairs, set wider apart than in XenopsyUa clieopis, and in front of 
this another comb of three or four pairs of hairs. What adds to the 
ragged appearance of the comb is the fact that the hairs project out¬ 
ward as well as backward, whereas in XenopsyUa cheopis (Fig. 4 a, 
a.c. and Fig. 6), Pulex irritans and Ctenocephalus canis they project 
TABLE IV. 
Differences in the Characters of the Terminal Somite ( Abd . 10) of the 
Larvae of the six Species investigated. 
Pulex irritans 
Anal comb of fine hairs 
Single; 11 (occasion¬ 
ally 10 or 12) pairs 
Ventro-lateral 
large hairs in 
series with the 
hairs of the 
anal comb 
5 pairs 
Anal struts as viewed 
from the side 
Thin, curved, tapering 
XenopsyUa cheopis 
Single: 11 (occasion¬ 
ally 10, 12 or 13) 
pairs 
2 or 3 pairs 
As in P. irritans, but 
rather blunter 
Ctenocephalus canis 
Single ; 11 (occasion¬ 
ally 12, rarely 13) 
pairs 
3 pairs 
As in P. irritans, but 
smaller 
Ceratophyllus fasciatus 
Double ; Principal 
corub of 7 pairs. 
Anterior comb of 4 
pairs 
3 pairs 
Thiele, straight or very 
slightly curved, only 
slightly tapered, 
blunt ended 
Ceratophyllus gallinae 
Double; principal 
comb of 5-8 pairs. 
Anterior comb of 
2-4 pairs 
3 pairs 
As in C. fasciatus 
Leptopsylla musculi 
Double; principal 
comb of 6-7 pairs. 
Anterior comb of 
3—4 pairs 
3 pairs 
As in C. fasciatus, but 
smaller 
backward only, and are thus parallel with one another. The bases of 
the hairs of the principal comb, also, in Ceratophyllus fasciatus, Cerato- 
phyllus gallinae and Leptopsylla musculi are not exactly in a line ; in 
some cases, indeed, the bases of the small hairs above the anal eminence 
are so irregular that they seem to be set in three rows rather than 
in two. 
