A. W. Bacot and W. G. Ridewood 
163 
from the smooth surface of the head are the setae, and the small processes 
around the bases of the antennae. The positions of the setae on the head, 
and their relative sizes, are shown in Figs. 1 and 2. 
Fig. 1. Head of larva of Xenopsylla cheopis ( x 110). A, right side ; B, dorsal aspect of 
a head with closed mouth; C, dorsal aspect of a head with the mouth open and the 
lip well extended. Drawn by camera lucida from unmounted specimens. W. G. R. 
a. antenna ; a.p. papillae around base of antenna ; l. upper lip or labrum ; l.p. labial palp ; 
m. mouth ; m.p. maxillary palp. 
TABLE I. 
Differences in the Characters of the Heads of the Larvae of the six Species 
investigated. 
Kelative size 
of head 
Snout as 
viewed 
from above 
Number of 
teeth on 
mandible 
Palp of 
first 
maxilla 
Papillae at 
base of 
antenna 
Pulex irritans 
large 
medium 
three 
type A 
type A 
Xenopsylla cheopis 
small 
narrow 
five 
(occasionally six) 
type A 
type A 
Ctenocephalus canis 
rather small 
medium 
six 
(occasionally five) 
type A 
type A 
Ceratophyllus fasciatus 
large 
broad 
eight 
type B 
type B 
Ceratophyllus gallinae 
large 
broad 
six 
type B 
type B 
Leptopsylla musculi 
medium 
broad 
eight 
(occasionally seven) 
type B 
type B 
