FLEAS. 375 



The flea has six legs. The first pair appears to be 

 joined to the head, but is fastened to the pro- 

 thorax. The hind legs are very large and strong, 

 and enable the flea to hop so well. All the legs are 

 furnished with hairs. 



The eggs (Plate 47, Fig. 3) are laid in dirt 

 in houses, buildings, and also in the fur of 

 animals such as cats, rabbits and dogs. They are 

 laid loosely in the fur, and may drop to the ground 

 as tlie animal walks. Of course, tliey are very tiny. 



The larva (Plate 47, Fig. 4) is worm-like. Sharp 

 describes the larva, when just hatched, as having 

 on its head a cuiious structure for breaking open 

 the egg shell. It has a biting mouth and 10 pairs 

 of spiracles, for breathing, along tlie side of the 

 body. It lives in refuse and dirt. Tlie pupa (Plate 

 47, Fig. 5) is enclosed within a tiny cocoon. 



TFe adult emerges within a fortnight. 



The house flea is Pitle.v irritans; the bird flea is 

 Piilex avium : Piilcx scrraticeps of dogs and cats — 

 but fleas seem to pass freely from one animal to 

 another. 



The fleas on rats may carry germs of disease. 

 In Sydney it was proved that rats carried the 

 germs of plague, and, with the temporary extermina- 

 tion of rats, the plague subsided. 



The Chigger or sand flea of tropical America is 

 a pest which buries its body in the flesh of man, 

 causing irritation and disease. 



