BEETLES. 553 



The wings of insects are furnished with a ramifying system of tubes, called 

 nervures. When the insect emerges from the pupa its wings are small and 

 limp ; but first fluid and then air is pumped through these 

 tubes, and the wing quickly grows to its proper size and Wings, 



dries. These nervures differ much in arrangement in differ- 

 ent insects, and are very useful in classification. The front of the wing is 

 called the costa, the part nearest to the body the base, the part opposite to 

 the body the hind margin or outer margin, and the part opposite the costa 

 the inner margin. The extremity of the costa is called the tip, and that of 

 the inner margin the hinder, or in the hind- wings the anal, angle. But these 

 divisions shade imperceptibly into each other in insects with rounded wings. 

 Between the bases of the fore- wings we sometimes find a triangular plate called 

 the scutellum. The hind- wings are often smaller, rounder, and of a different 

 consistency to the fore-wings, but when the fore-wings play the part of wing- 

 cases, under which the hind-wings are folded, the latter are often much 

 larger. Many insects possess the power of leaping, in which case the hind 

 legs are often very long, or the coxae and femora are much thickened. 



Insects are divided into several large orders, of which the following are 

 the principal ones : 



I. COLEOPTERA (Beetles). Insects with mandibles ; fore- wings (called 

 elytra) horny or leathery; wings membranous, folded and doubled 

 beneath them. 



II. ORTHOPTERA (Grasshoppers, etc.). Insects with Orders of 

 mandibles ; fore- wings (called tegmina) leathery; Insects, 

 hind- wings folded fan-like beneath them. 



III. NEUROPTERA (Dragonflies, etc.). Insects with mandibles (some- 



times very imperfectly developed ; wings with many nervures ; 

 membranous and naked, or clothed with hairs. 



IV. HYMEN OPTERA (Bees, Wasps, Ants, etc.). Insects with mandibles, 



and often a proboscis ; wings membranous, rather small, with 

 few nervures ; the fore and hind-wings often connected together 

 by a series of little hooks. 



V. LEPIDOPTERA (Butterflies and Moths). Insects with a sucking pro- 

 boscis, and membranous wings clothed with scales. 



VI. HEMIPTERA (Bugs and Froghoppers). Insects with a sucking pro- 

 boscis, fore- wings leathery or membranous (or membranous only 

 at the tips) ; hindwings membranous. 



VII. DIPTERA (Flies). Insects with a sucking proboscis, and only one 

 pair of membranous wings. 



The first four orders are sometimes called Insecta Mandibulata, and the 

 three last Insecta Haustellata. 



Fuller characters for these orders will be given in their places. There are 

 also some groups of insects (chiefly apterous) which will not fit very well 

 into any of these orders, and which will be noticed separately. 



ORDER COLEOPTERA (BEETLES). 



The Coleoptera are physically among the most highly organised insects, 

 although they cannot compare with the ffymenoptera in intellectual devel- 

 opment. They are distinguished by having four wings, the first pair of 



