248 ANNUL AT A. 



or potato-beetle works untold mischief in potato fields, the 

 larva feeding upon the leaves. The whole development is 

 accomplished in four weeks and the fecundity is very high. 

 Other interesting beetles are the burying-beetles which bury 

 the bodies of small animals as food for their larvae, the 

 useful " lady-birds " which feed on green aphides, and the 

 various water-beetles which have aquatic larvae. 



Fig. 166. — A Water-beetle (Dytisais ?narginalis). 



A, The aquatic larva with soft body. 



Order II. — Hymenoptera. 



The metamorphosis is complete, the mouth parts are 

 modified for biting and licking and there are two pairs of 

 membranous wings. There is no one popular name for 

 the Hymenoptera^ but they include the Ants, Bees, Wasps 

 and Gall-flies. The " biting and licking " mouth parts are 

 well illustrated by those of the bee. The mandibles are of 

 the biting and crushing type, and the first maxillae form a 

 pair of semi-cylindrical tubes enveloping the labium. The 

 maxillary palps are vestigial. The labial palps are long 

 and the end of the labium is produced into a long flexible 

 hairy " tongue " or ligula. It can be withdrawn inside the 

 basal part of the labium. The maxillae form a suctorial 

 cylinder and the ligula serves to lick honey and pollen. 



The Hymenoptera are of special interest from their social 

 habits. Ants, bees and wasps of many species live in 

 communities in which there is structural and physiological 

 division of labour. In the case of the bees there can be 

 distinguished the males or drones, the female or queens, 



