INSECTS. FLEA. 325 



pupa form, wliich it retains for four days ; and in nine days more it 

 becomes a perfect flea. The head of the flea found in the cat (No. 3, 

 fig. 157) is seen to be very different in its form from that of the 



fig. 156. 



1. Female Flea. 2. Male Flea. 



Tlie small circles enclose the little animalB of the natural size. 



human flea (fig. 156). Its jaws are supplied with formidable booklets, 

 and from the first and second joints behind the head project short and 

 strong spines ; these are, no doubt, for the purpose of enabling it to 

 maintain a firmer and better hold on the animal. 



