166 
Larvae of Fleas 
In Table I the number of the teeth includes the terminal, forwardly- 
directed tooth. Pulex irritans has three fairly stout teeth on each 
mandible; in the other species the teeth are smaller (see Fig. 3). 
In Xenopsylla cheopis there are five, occasionally six ; in Ctenocephalus 
canis six, occasionally five ; in Ceratophyllus fasciatus usually eight, 
sometimes seven ; in Ceratophyllus gallinae usually six; and in Lepto- 
psylla musculi eight, occasionally seven. 
The same mandible differs greatly in appearance according to the 
particular angle at which the row of teeth is viewed ; in the sketches 
reproduced in Figure 3 the mandibles are as far as possible so 
orientated that the lateral teeth are at right angles to the axis of vision, 
i.e. they appear as little fore-shortened as possible. In Leptopsylla 
musculi the mandible is rather narrower than in Ceratophyllus fasciatus, 
and the teeth appear less crowded towards the front end of it, although 
in both cases the teeth extend over about one-third of the length of the 
mandible. 
Maxillae. 
The maxillae (first maxillae) have the form of a pair of brushes, 
like hair-brushes, but with the bristles restricted to the antero-median 
half of the upper surface. The bristles are mostly short and curved, 
but there are at the front of each brush two short, forwardly directed, 
straight hairs which are two-jointed. The maxillary brushes work 
against two patches of oblique, curved hairs in the roof of the mouth. 
The two maxillae, with the labium between them, form the floor of the 
front part of the mouth. Kunckel supposed that each maxilla was 
like a part of a circular saw, cutting by its edge only (1873, p. 138 and 
Plate VI, Figs. 7 and 11) ; he evidently failed to notice the bristles that 
are directed upwards into the mouth-cavity. 
Projecting from the antero-ventro-external part of the maxilla is 
the maxillary palp (Figs. 1 and 2, m.p.), which arises from a broad 
shallow depression, and consists of two joints. There are among the 
six species of larvae studied two distinct types of maxillary palp. In 
the first type, which we may call type A, the basal joint is short and 
broad, and stands higher on one edge than the other ; the second joint 
is narrower at its base than at its free end, its end is obliquely truncated, 
and bears five small points, more or less radiating. In the second type, 
or type B, the basal joint is cylindrical, about twice as long as broad and 
square-cut at the end ; the second joint is much narrower than the first, 
is cylindrical, rounded at the end, and bears four or five very minute 
