CHAPTER XV 



THE SAW-FLIES, ICHNEUMONS, WASPS, BEES, AND ANTS 

 (HYMENOPTERA) 



Characteristics. Insects with four membranous wings, with few cross-veins, 

 the hind-wings smaller than the fore-wings ; mouth-parts, formed for both biting 

 and sucking, or lapping ; abdomen of the females, usually bearing an ovipositor 

 or sting ; metamorphosis, complete. 



The insects of this order are mostly beneficial, though a few 

 families are injurious to crops. Probably no other invertebrate ani- 

 mals, and very few vertebrates, have as highly developed instincts 

 as many of the insects of this order, the social ants, bees, and 

 wasps having always been the objects of the greatest popular and 

 biological interest on account of their high intelligence, if it may 

 be so termed. 



The wings are membranous, with but few veins, are frequently 

 clothed with short hairs, and are held together by a row of hooks 

 on the anterior margin of the hind-wings, which grasp a fold of 

 the hind-margin of the fore-wings, so that the two wings move to- 

 gether as one. The name of the order is derived from hymen (a 

 membrane) and pteron (a wing). The mandibles are always well 

 developed and used for biting. In the ants, bees, and wasps the 

 maxillae are more or less developed as a sheath surrounding the 

 labium, which is prolonged into a tongue, so that these mouth- 

 parts are adapted for sucking or lapping the liquid food. 



Most of the larvae are footless and maggotlike, living within the 

 food, where the eggs are placed by the adults, but the larvae of the 

 first two families bear both true legs and several pairs of abdominal 

 prolegs, and resemble caterpillars in both form and habits. Many 

 species spin a cocoon before pupating, and the newly formed pupae 

 are white, with the legs, wings, and antennae pressed close to the 

 body. 



The different families fall into several natural groups recogniz- 

 able by their structure and habits. 



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