VI HYMENOPTERA 245 



the portion of abdomen immediately behind this first segment is con- 

 stricted to form a slender "waist," which therefore does not mark, as 

 one might have expected, the boundary between abdomen and thorax. 

 In certain of the Wasps this waist is very long and slender. These wasps 

 frequently exhibit very interesting habits inasmuch as they store the 

 nests in which they lay their eggs with spiders, or caterpillars or other 

 insects, which they have completely paralysed by stinging, so that the 

 young wasp on hatching finds ready at hand an abundant supply 

 of fresh, indeed living, food. In some cases it has been observed 

 that the wasp is able with great skill to insert the sting straight into 

 the main nerve-ganglia of the victim so as to ensure its complete 

 paralysis. 



The Formicidae or Ants in their large and complex communities show, 

 in addition to the high degree of specialization already alluded to, a 

 highly complex social organization and many wonderful abilities and 

 habits. Some of the South American ants inhabiting districts liable to 

 inundation construct special refuges in trees to which they retire during 

 the floods. Oecophylla in Ceylon uses its own larva, with its silk-glands 

 opening at the head end, as an animated tube of cement to fasten together 

 the edges of leaves curled' into tubular shelters. Polyergus of Europe 

 and America raids the nests of certain other ants and carrying off their 

 larvae and pupae rears them as slaves : they have in the course of ages 

 become so dependent on their slaves as to have actually lost their power 

 of feeding their own young. Another common European ant of the 

 genus Lasius keeps domesticated aphides which provide it with sweet 

 honey-dew. Atla, a large black ant of the American continent, cuts 

 disc-like pieces out of the leaves or petals of trees which it conveys into 

 underground excavations and there uses as a nutritive medium on which 

 to cultivate a particular species of fungus. The ants are able in some 

 way to modify the growth of the fungus so that it forms spongy masses 

 which serve as food for the community. The ants of the American 

 genus Eciton are remarkable from the fact that the community does not 

 form a permanent abode but merely temporary camps in hollow trees, 

 under logs, or in other suitable situations. Normally the community is 

 on the march, spreading over a considerable area of ground and consuming 

 everything eatable it encounters. 



The main features of the Ljepidoptera — Butterflies and Moths — have 

 already been mentioned under such headings as wings, mouth-parts, and 

 metamorphosis. In the larva glands, probably corresponding with the 

 salivary glands of other insects, open on a projecting papilla about the 

 middle of the labium. The secretion as it issues from the gland hardens 



