162 INSECT TRANSFORMATION 



to side, its small rounded head and its elongate spiny legs is 

 highly characteristic. Eyes, as in the Anoplura and Mallo- 

 phaga, are absent entirely, or much reduced. The short, 

 stout feelers (Fig. 92 b) are sunk in pits on either sides of the 

 head ; the feeler has two relatively broad basal segments, 

 succeeded by possibly ten, short and still broader segments, 

 crowded together and imperfectly distinguished from each 

 other, forming a terminal club. The upper lip (labrum) and 

 the mandibles are elongate piercers with saw-teeth on their 

 edges, forming in combination a suctorial tube and lying 

 between and in front of the short flattened maxillae, each with 

 its four-segmented palp ; these palps project conspicuously 

 downwards and forwards from the head, looking like feelers 

 (Fig. 92 c). The labium (d) is prolonged into a " beak " and 

 bears a pair of thickish palps which serve as sheaths for the 

 piercing organs of the mouth. Thus the flea is admirably 

 provided for its occupation of blood-sucking. The thoracic 

 segments often bear rows of spines (" combs ") and sometimes 

 small scale-like plates, which have been regarded, though 

 doubtfully, as vestigial wings. The spiny legs are remarkable 

 for the relatively enormous size of their haunches (coxae) and 

 their strong claws ; fleas are thus adapted for leaping from 

 one host to another and for clinging to the host's hairs or 

 feathers. 



Fleas' eggs (Fig. 92 e) are oval in shape, with smooth, white 

 cases, which often resemble birds' egg-shells in miniature. 

 They are not, like the eggs of lice, fastened to the host's hairs, 

 but fall into crevices of its nest or dwelling-place. From these 

 eggs are hatched after a few days eruciform larvae (Fig. 92 /) 

 with distinct head and fourteen body-segments, which are 

 destitute of legs, but bear tubercles with long bristles, while 

 outgrowths possibly suitable for adhesion, are present at the 

 tail-end. The newly-hatched flea-grub may possess a spine 

 on the head which serves to break the egg-shell ; this structure 

 is not present in the later larval stages, of which there are two 

 or three. The flea-grub's head (Fig. 92 g) bears short feelers 

 and biting mandibles, by means of which it feeds on organic 

 particles in the nest or other matter among which it lives. 

 The larva of Pulex irritans, the flea which commonly infests 

 mankind, lives in the crevices between the boards of floors 



