1408 THE STORY OF THE UNIVERSE 



work of another species, the Cynips longipennis. 

 One curious point about this group is, that in some 

 of the commonest species the females alone are 

 known, no one yet having ever succeeded in find- 

 ing a male. 



Another great family of the Hymenoptera is that 

 of the ichneumons; the females lay their eggs either 

 in or on other insects, within the bodies of which the 

 larvae live. These larvae are thick, fleshy, legless 

 grubs, and feed on the fatty tissues of their hosts, 

 but do not attack the vital organs. When full- 

 grown, the grubs eat their way through the skin of 

 the insect, and turn into chrysalides. Almost every 

 kind of insect is subject to the attacks of these little 

 creatures, which are no doubt useful in preventing 

 the too great multiplication of insects, and especially 

 of caterpillars. Some species are so minute that 

 they actually lay their eggs within those of other in- 

 sects. These parasites assume very curious forms in 

 their larval state. 



But of all the Hymenoptera, the group containing 

 the ant, the bee, and the wasp is the most interesting. 

 This is especially the case with the social species, 

 though the solitary ones also are extremely remark- 

 able. The solitary bee or wasp, for instance, forms 

 a cell generally in the ground, places in it a sufficient 

 amount of food, lays an egg, and closes the cell. In 

 the case of bees, the food consists of honey; in that 

 of wasps, the larva requires animal food, and the 

 mother therefore places a certain number of insects 

 in the cell, each species having its own special prey, 

 some selecting small caterpillars, some beetles, some 



