12 INTEODUCTION. 



gceidce, Cimicidce, Eeduviada, Hydrometradoe, Nepadce [Plate I. 

 Fig. 1, Nepa apiculata], and Notonectadce) live entirely on the 

 juices of animals, and by this means destroy great numbers of 

 noxious insects ; some are of much service in the arts, affording us 

 the costly cochineal, scarlet grain, lac, and manna ; but the benefits 

 derived from these are more than counterbalanced by the injuries 

 committed by the domestic kinds, and by the numerous tribes of 

 plant-bugs, locusts or cicadai, tree-hoppers, plant-lice, bark-lice, 

 mealy bugs, and the like, that suck the juices of plants, and re- 

 quire the greatest care and watchfulness on our part to keep them 

 in check. 



4. Nedeoptera (^Dragon-flies, Lace-winged flies; May- 

 flies, Ant-lion, Bay-fly, White Ants, ^c). , Insects with jaws, 

 four netted wings, of which the hinder ones are the largest, 

 and no sting or piercer. Transformation complete, or partial. 

 Larva and pupa various. 



The white ants, wood-lice, and wood-ticks, {^Termitidce and 

 PsocidtB,) the latter including also the little ominous death-watch, 

 are almost the only noxious insects in the order, and even these 

 t!o not injure living plants. The dragon-flies, or, as they are com- 

 monly called in this country, devil's-needles (Libelluladas), (Figs. 

 4, 5,) (Plate I. Fig. 2, Agrion basalis,) prey upon gnats arid 

 mosquitoes ; and their larvfe and pupae, as well as those of the 

 day-flies {Ephemeradce), semblians (SemblididcB), and those of 

 some of the May-flies, called caddis-worms (PkryganeadcB), (Fig. 

 6,) all of which live in the water, devour aquatic insects. The 

 predaceous habits of the ant-lions {Myrmeleontidce), (Fig. 7,) 

 have been often described. The lace-winged flies (Hemerobi- 

 ada), (Fig. 8,) in the larva state, live wholly on plant-lice, great 

 numbers of which they destroy. The mantispians {Mantispa- 

 dm), and the scorpion-flies {Panorpadce), are also predaceous 

 insects. 



5. Lepidopteea {Butterflies and Moths'). ]Mouth with a 

 spiral sucking-tube ; wings four, covered with branny scales. 

 Transformation complete. The larv.ic are caterpillars, and 

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



