They are divided into several tribes and many families. TRIBE I.--ORNOPTERA OR DRAGON FLIES. To this tribe belong the Dragon Flies, the largest and most beautiful members of the whole order. About 1,500 species have been described from various parts of the world, and of these about fifty are known to inhabit our own country. Their habits are very much alike. The insect passes all the earlier stages of its existence in water. The _larvæ_ are most voracious creatures, and are undoubtedly the most predaceous of insects. The apparatus by which they capture their prey consists of a peculiar modification of the _labium_. When full grown the _larvæ_ crawl up the stem of some aquatic plant out of the water, and after resting there for a longer or shorter time the skin splits open along the thoracic region, and the perfect insect by degrees struggles out of its investment, and when the wings are dried it starts off to continue the same scene of rapine which has characterised its subterranean existence. The perfect insect may be seen hawking about for insects in the neighbourhood of pools in all fine weather during the summer and autumn months. In dull weather, however, they usually remain at rest on the leaves of plants and trees, etc. The eyes of Dragon Flies are most beautiful objects when viewed under the microscope; they are composed of a great number of facets or lenses. In one species of Dragon Fly as many as 10,000 of these facets have been counted in each of its eyes. Besides these compound eyes most dragon flies have additional eyes, called _Ocelli_, which are situated on the top of the head; they are, however, quite simple. It is commonly thought by persons who are not naturalists that dragon flies sting; such an erroneous idea we take the opportunity to correct. [Illustration: Fig. 54.--Libellula Depressa.] The _Ornoptera_ are divided into two principal families. _Family 1, Libellulinæ._--To this family belong all the great dragon flies, mostly thick-bodied insects. It is subdivided into four sub-families. To the first sub-family, the _Libellulidæ_, many common and familiar dragon flies belong. The best known is what is vulgarly called the "Horse-stinger" (_Libellula depressa_), an insect about two inches long, with a rather depressed abdomen, which is yellowish-brown, with yellow spots on the sides in the female, and coated with a beautiful violet-blue powder in the male. It may be seen almost everywhere, hawking for flies about rivers and ponds, during warm weather. The second sub-family, the _Cordulidæ_, contains four British species, of which the beautiful _Cordulia metallica_ is the typical example. The _Æschnidæ_ contain some of the largest members found. The great dragon fly (_Æschna grandis_) is one of these. It is nearly three inches long and four inches in expanse of the wings, and is of a light rusty-brown colour with a few pale markings. Of the _Gomphidæ_ only four species inhabit our own country.