HYMENOPTERA 



37 



Fig. 37. — The saws of a 

 sawfly. Enlarged and nat- 

 ural size. Original. 



Adults in this order are characterized by the possession of two 

 pairs of wings, both pairs membranous, the front pair larger than 

 the hind pair. The mouth parts are com- 

 plex, and are adapted for biting and for 

 sucking. However, the structure of the 

 mouth parts is not usually of direct eco- 

 nomic importance, since the adults do not 

 habitually feed on or destroy that which is 

 of value to man. 



In one subgroup of the Hymenoptera the 

 abdomen of the adult is broad at the 

 point where it joins the thorax; in other 

 words, the insects are " broad waisted." 

 This section includes the Tenthredinidai or 

 sawflies, a family containing many injurious 

 species. The name sawfly is given to this 

 family because the end of the abdomen in the adult female is provided 

 with genuine saws, which it uses in making a place for the deposition 

 of its eggs. Sawfly larvae strongly resemble the larva? of the Lepi- 

 doptera, but may be distinguished from them by the number of pro- 

 legs — the false legs situated behind the three pairs of genuine legs 

 near the front end of the body. The larva^ of sawflies usually have 



six to eight pairs of these pro- 

 legs, while those of the butterflies 

 or moths have never more than 

 five pairs. Examples of injurious 

 sawflies are seen in the pear slug 

 and the currant worm. 



A closely related subgroup of 

 the Hymenoptera comprises a 

 number of families in which the 

 female is pro^^ded with a boring 

 apparatus at the hind end of the 

 abdomen. These families include some of our important beneficial 

 species living as parasites in the bodies of other insects, the Ichneu- 



FiG. .38. — An ichneumon 

 Original. 



Pimpla. 



