_Ventral._ On the under-side, the insect being in its proper position. NEW ZEALAND SCALE-INSECTS (COCCIDIDÆ). CHAPTER I. INTRODUCTORY. Insects are divided by naturalists into several principal orders, the distinguishing marks of which are generally very well defined--for example, the butterflies and moths belong to the order _Lepidoptera_, the dragon-flies to the _Neuroptera_, the common house-flies to the _Diptera_, and so on. These orders are founded upon the characters and arrangement of the wings. They are subdivided into families, and these again into genera and species. One of the orders is that of the Hemiptera, which is composed of the two following sections:-- Hemiptera-Heteroptera, including the bugs, water-beetles, &c. Hemiptera-Homoptera, including the crickets, cuckoo-spits, plant-lice (Aphides), leaf-hoppers (Psyllids), scale-insects (Coccids), &c. The insects treated of in this volume are therefore placed as follows:-- Class--Insecta. Order--Hemiptera. Section--Homoptera. Family--Coccididæ. The genera and species will be found in their places. The common English name for this family--"scale-insects"--is not very appropriate. Some few of them have the appearance of small thin scales on leaves or twigs, but many have not. Nor are the German appellations--"gall-insekten" or "schild-lause"--more appropriate. Gardeners have given to some of them the name of "mealy-bug," which, although decidedly neither elegant nor euphonious, very fairly represents the character of that particular portion of the family. The origin of the name "Coccididæ," or, as abbreviated often in this volume, "Coccids," is found in the old Greek word "[Greek: kokkos]," denoting a rich red dye, which was much admired by the Greeks and Romans, and which was procured from the insect now known as _Kermes vermilio_ (the _Coccus ilicis_ of Linnæus). When the cochineal insect was discovered in Mexico it soon overpowered all the others, producing commercial dyes, and from it has come the title "Coccid," now applied to the whole family. Cochineal itself has of late years been pushed aside to a great extent by the aniline (coal-tar) dyes; yet it is still used for many purposes. This insect lives on the leaves of cactus. Amongst the New Zealand species described in this work will be found one, _Dactylopius alpinus_, which produces a red dye similar to, though probably not equal to, cochineal. Before the discovery of aniline dyes it might possibly have been worth while to cultivate this insect for its dye; but this would scarcely answer now.