390 
Biology of Phthims pubis 
apex, the grasp of the individual legs being comparable to that of a 
threaded needle whose eye is incomplete. Direct efforts to pull the 
insect away may result in a leg or two being torn off, the limb being 
left clinging to the hair. That such maiming takes place in nature is 
evident from specimens I have collected^. 
The accompanying illustration (Fig. 1) shows that the front legs of 
Phtliirus are relatively feeble and sharp-clawed, the second and third 
leg-pairs being on the contrary stout, their claws terminating in a 
aspect. 
rounded knob. The difference between Phtliirus and Pediculus in respect 
to the leg structure will be seen at a glance by comparing Figs. 1 and 2 
in which I have shown the claws in black. The sharp and less incurved 
claws of Pedicvlus explain why it can progress readily on hairless 
surfaces, and the corresponding structures in Phtliirus show why it is 
so helpless when removed from hair, the four hind legs being adapted 
solely for locomotion on hair, whilst the feeble first leg-pair play a very 
inconsiderable part in progression. In short, the crab-louse, as its 
^ In a maimed specimen (5 D) that was raised experimentally, two lost legs (pairs 
I and ii) were not regenerated during metamorphosis from the (injured) second stage 
larva to adult. 
