14 INTRODUCTION. 



Pupa with the cases of the wings and of the legs indistinct, 

 and soldered to the breast. 



Some kinds of caterpillars are domestic pests, and devour cloth, 

 wool, furs, feathers, wax, lard, flour, and the like ; but by far the 

 greatest number live wholly on vegetable food, certain kinds being 

 exclusively leaf-eaters, while others attack the bud;-, fruit, seed?, 

 bark, pith, stems, and roots of plants. 



6. HYMENOPTERA (Saw-flies, Ants, Wasps, Bees, $c.~). 

 Insects with jaws, four veined wings, in most species, the 

 hinder pair being the smallest, and a piercer or sting at 

 the extremity of the abdomen. Transformation complete. 

 Larvae mostly maggot-like, or slug-like ; of some, caterpillar- 

 like. Pupae with the legs and wings unconfined. 



In the adult state these insects live chiefly on the honey and 

 pollen of flowers, and the juices of fruits. The larvae of the 

 saw-flies ( Tenthredinidce), under the form of false-caterpillars and 

 slugs, are leaf-eaters, and are oftentimes productive of much injury 

 to plants. The larva? of the xiphydrians (XiphydriadtE), and of 

 the horn-tails ( Uroceridce), are borers and wood-eaters, and con- 

 sequently injurious to the plants inhabited by them. Pines and 

 firs suffer most from their attacks. Some of the warty excres- 

 cences on the leaves and stems of plants, such as oak-apples, gall- 

 nuts, and the like, arise from the punctures of four-winged gall-flies 

 (Diplolepididce), and the irritation produced by their larvae, which 

 reside in these swellings. The injury caused by them is, com- 

 paratively, of very little importance, while, on the other hand, 

 we are greatly indebted to these insects for the gall-nuts that are 

 extensively used in coloring and in medicine, and form the chief 

 ingredient in ink. We may, therefore, write down these insects 

 among the benefactors of the human race. Immense numbers of 

 caterpillars and other noxious insects are preyed upon by in- 

 ternal enemies, the larvae of the ichneumon-flies {Evaniadce, Ichneu- 

 monida:, and Chalcididte), which live upon the fat of their victims, 

 and finally destroy them. Some of these ichneumon-flies (Ichneu- 

 mones ovitlorum*) are extremely small, and confine their attacks 



* Now placed among th.e Proctotnipidce. 



