A. W. Bacot and W. Gr. Ride wood 
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points (see Figs. 1 and 2, m.p.). The palps of the A type occur in 
larvae of Pulex irritans, Xeno])sylla cheopis, and Ctenocephalus canis ; 
those of type B are found in Ceratophyllus fasciatus, Ceratophyllus gal- 
linae and Leptopsylla musculi. It is of interest to note that this division 
of the six species into two groups according to the characters of the 
maxillary palps is supported by details of internal anatomy. The 
salivary glands of the first three species, for instance, have only two 
lobes, while those of the last three species have three. 
We have not examined the larvae of Ctenocephalus felis, but, as¬ 
suming that they do not differ materially from those of Ctenocephalus 
canis —some authorities have denied that the species are distinct, 
although the differences in the shape of the head and details of the male 
genitalia of the adults are at the present time considered of adequate 
specific value—the figures given by Laboulbene (1872, PI. XIII, Figs. 5, 
9, 10, 13) show the basal joint much too narrow and the terminal points 
in too regular a row, while in Kiinckel’s figure (1873, PI. VI, Fig. 7) the 
maxillary palp is distinctly of the B type, and since he was also studying 
larvae of Ceratophyllus fasciatus at the time, the suggestion that we offer 
is that his Figure 7 represents a ventral view of the mouth of Cerato¬ 
phyllus fasciatus, and not of Ctenocephalus felis. This suggestion is 
supported by the sharpness and the length of the papillae around the 
base of the antenna in Figure 7, whereas in his Figure 8 the papillae are 
short and rounded, as we find them to be in Ctenocephalus canis. 
In an unmounted head the maxillary palps of a larva that has died 
with the mouth open project in front of the upper lip (see Figs. 1 c 
and 2 A, m.p.). The maxillae are particularly large and prominent 
in Leptopsylla musculi. If the larva has died with the mouth slightly 
closed, the labium and the maxillae, as seen in a side view of the head, 
are much retracted, and their external surfaces are disposed in an oblique 
line extending from the labial palps to the front point of the snout. 
Labium. 
The labium, a median structure representing the second pair of 
maxillae, is set in the floor of the mouth, between the two maxillary 
brushes. It tapers forward to a blunt point, and has the extremity 
bent downward. Projecting downward from the under surface of the 
base of the labium is the pair of labial palps, each of which consists 
of a short basal joint bearing at its extremity four stout bristles. These 
bristles do not taper ; two are short, about three or four times as long 
