98 A BOOK OF INSECTS 



food brought to it by the " workers " of the community. 

 The sub-order includes many families, among which the 

 following are most important. 



The gall- wasps (Cynipidce) are small, dark-coloured 

 insects, most of which lay their eggs in the tissues of 

 plants, and give rise to galls. Some of the species, how- 

 ever, are parasites, while others are inquilines — i.e. they 

 lay their eggs in galls which have been induced by other 

 species. 



The ichneumons make up the large families Ichneu- 

 monidce and Braconidce. The females lay their eggs 

 in the bodies of caterpillars, upon which the larva 1 

 feed as parasites. Some species, which attack wood- 

 burrowing grubs, possess exceptionally long ovipositors, 

 and thrust these implements through the solid timber in 

 order to reach their victims. The full-fed larvae leave the 

 body of their host, and spin cocoons, before changing 

 to pupae. 



The Chakididce and Proctotrypidce are enormous 

 families of minute insects, most of which are parasitic in 

 their early stages of development. Many species attack 

 caterpillars. Others lay their eggs in galls, or in the nest- 

 cells of the higher Hymenoptera, and their grubs prey 

 upon the contained larvae. Many of the Proctoti'ypidce 

 are egg parasites — i.e. they lay their eggs in those of 

 larger insects. The Chalcididce include a remarkable 

 group of gall-forming species known as fig-insects, of 

 which more anon. 



The ruby wasps {Chrysididce) are remarkable for their 

 brilliant blue, green, or crimson hues. They are often 

 called " cuckoo wasps," because the females lay their eggs 

 in the nest-cells of other Hymenopterous insects, where 

 the Chrysid grub feeds upon the contained food or upon 

 the rightful occupant. 



