26 AN ACCOUNT OF BRITISH FLIES. 
it seems improbable that they can all find human hosts, or even 
sufficient vertebrates of any kind. 
It is said that the species that is found in the dog is different to 
the one found in man. Whether the species in Africa is different 
to that in America I do not know. 7 
This was the insect that Waterton found so troublesome during 
his “ Wanderings.” 
Anatomy of the Larva of Pulex. 
In all the species there is a slight difference in the form of the 
larvee, but the general arrangement is the same. The type we take is 
Fic. 4.—Head of Larva of P. felis.—is, upper lip; a, antennz ; m, maxillz ; 
mb, mandibles ; ~i, pharynx; A, maxille, and B, mandibles, greatly enlarged. 
the larva of P. felis, parasitic on the cat. This subject has been 
fully worked out by Laboulbéne and Kunckel, and their researches 
published in the “ Annals of the Entomological Society of France” 
(2 and 3). The larva, which may attain the length of a quarter of 
an inch, is usually of a whitish colour, and in some cases so trans- 
parent as to allow the alimentary canal to be examined through the 
integuments (Fig. 1). 
The number of body-segments is thirteen, and each is armed by 
a few setaceous hairs. The last segment is armed also by two 
strong recurved claws. The head is corneous, and presents certain 
peculiarities. The antenne are a fair size; their structure can be 
seen from the figure (4). There is also developed a pair of maxillz, 
with serrated edges, and also a pair of mandibles. The large upper 
