INTRODUCTION. 13 



have six true legs, and from four to ten fleshy prop-legs. Pupa 

 with the cases of the wings and of the legs indistinct, and sol- 

 dered 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 buds, fruits, seeds, 

 bark, pith, stems, and roots of plants. 



6. — Hymenoptera (Saw-Jlies, Ants, Wasps, Bees, &fc.). 

 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 mag- 

 got-like, or slug-like, of some, caterpillar-like. Pupse 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 ( Ten- 

 lliredinidoi), under the form of false-caterpillars and slugs, are leaf-, 

 eaters, and are oftentimes productive of much injury to plants. The 

 larvae of the xyphydrians (XiphydriadcB), a.nd of the horn-tails ( C/roce- 

 ridce), are borers and wood-eaters, and consequently injurious to the 

 plants inhabited by them. Pines and firs suffer most from their attacks. 

 Some of the warty excrescences on the leaves and stpms of plants, 

 such as oak-apples, gall-nuts, and the like, arise from the punctures of 

 four-winged gall-flies {Diplolepididcs), and the irritation produced by 

 their larvae, which reside in these swellings. The injury caused by 

 them is, comparatively, 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 internal 

 enemies, the larva? of the ichneumon-flies {Evaniadce, Ichneumonidce, 

 and Chalcididce), which live upon the fat of their victims, and finally 

 destroy them. Some of these ichneumon-flies (Ichneumones ovulo- 

 rum*) are extremely small, and confine their attacks to the eggs of 

 other insects, which they puncture, and the little creatures produced 



* Now placed among the Proctotrupidce. 



