THE FOOD OF ANIMALS 



Fig. 393, — The Common Flea {Pulex irritans) 



On the left are the piercing mouth-parts. On the right, 

 larva (above) and pupa (below). Enlarged to various 

 scales. 



The Forest-Flies {Hippoboscid(B) are curious Diptera, parasitic 

 on the bodies of various warm-blooded animals, and presenting" 

 us with a series of species showing the gradual degeneration and 

 disappearance of the wings. This is interesting because it helps 

 to throw light on those unpleasant and familiar creatures called 

 Fleas, which are very likely to be looked upon as wingless 

 Diptera, of which the remote ancestors possessed wings. The 



best-known species is the ubi- 

 quitous Common Flea {Pulcx 

 irritans) (fig. 393), but Mam- 

 mals and Birds are infested by 

 numerous other kinds, it being 

 a common error to suppose there 

 is but one sort of these crea- 

 tures. The piercing and suck- 

 ing mouth-parts differ in some 

 respects from those of Gnats, 

 &c. The long, pointed labrum is grooved on its under side, and 

 is closely applied to the hard, piercing mandibles, while a sheath 

 is formed by the two pairs of maxillae. 



The Fringe-winged Insects (Thysanoptera) in'clude minute 

 forms which feed on plants, and therefore do not require notice here. 



BUGS (Hemiptera) 



In this, the last order 

 of insects, are included a 

 great variety of forms, 

 such as bugs, aphides, 

 true lice, &c., most of 

 which are terrestrial, 

 though a fair number 

 are aquatic. The food 

 may consist of the juices 

 of animals or the sap of 

 plants, and in either case 

 the mouth - parts are 

 adapted for piercing and 



Fig. 394- 



-Mouth-parts of a Tree-Bug [Cicada), enlarged: ant., 

 antennas; u.L, upper lip. 



sucking, though constructed on a somewhat different type from that 

 described for the Diptera. Examination of one of these creatures 

 (fig. 394) reveals the presence of a piercing beak, which consists of 



