248 ANNULATA. 
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 larve, the 
useful “‘lady-birds ” which feed on green aphides, and the 
various water-beetles which have aquatic larve. 
Fig. 166.—A WATER-BEETLE (Dytiscus marginalis ). 
aA, The aquatic larva with soft body. 
OrvER II.—Hymenopeera. 
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 Aymenoptera, 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 maxillz 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 Zigwla. It can be withdrawn inside the 
basal part of the labium. The maxille 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, 
