that spi^ead Disease. 



bey 



that they may be readily compared with the corresponding parts 



of the male. 



Models are also shown of the egg and larva of the tropical rat- 

 flea, enlarged 150 diameters. The eggs of fleas are eUipsoidal in 

 shape, similar at the two ends, and of a translucent appearance, 

 suggesting thin china. The eggs laid by the rat-flea fall out of the 

 fur of the host, and remain on the ground, usually within the 



Fig. 9. — Tropical Rat-Flea, 

 Xenopsylla cheopls, male, X 36 ; largely responsible for the spread of plague. 



nest, run or burrow of the rat, until in about a week they hatch 

 out into active, maggot-like larvae. 



The larvae of fleas are not parasitic ; they live on the ground 

 either in the nest or the run of the host, and feed on all kinds of 

 refuse that may occur there, their mouth-parts being adapted for 

 chewing, and unlike those of the adult. They have no eyes, and 

 no legs, but move about by means of the hairs or bristles projecting 

 from the body, and the pair of processes or " struts " at the hind 

 end. After spinning cocoons and passing through a pupal or 



D 



