The _Neuroptera_ are not a very numerous body of insects compared with either the _Coleoptera_ or _Lepidoptera_, but they contain some of the largest and most handsome insects known. The order is very well represented in the temperate zones, though the finest species are met with in the tropical parts of the world. Nearly 700 species are known to inhabit the British Isles. In the whole world their number may be given in round figures at about 4,000, but there is no doubt that this number may be considerably increased. The largest and most handsome species are the Dragon Flies or _Ornoptera_, one species occurring in our own country, measuring fully four inches in expanse of the wings. The Lacewing Flies (_Hemerobiidæ_), the Day Flies (_Ephemeridæ_), the Stone Flies (_Perlidæ_), and the Caddis Flies (_Trichoptera_), are among the other more conspicuous members of the group. [Illustration: Fig. 42.--Nemoptera Extensa.] The _Neuroptera_ may be divided into three great sub-divisions, according to certain well-defined characteristics. The modern tendency is to raise each of these sub-divisions to the rank of orders. The _Neuroptera_ may be classified as follows:-- _Sub-Order 1, Planipennia_, or true Neuroptera. Metamorphoses complete, larvæ, mostly terrestrial. _Sub-Order 2, Trichoptera_, or hairy-winged Neuroptera. Metamorphoses complete, larvæ aquatic. Wings of Imago clothed with hairs. _Sub-Order 3, Pseudo-Neuroptera_, or false Neuroptera. Metamorphoses incomplete. The most important distinction between the first two groups and the third is that the former undergo complete metamorphoses, whereas in the latter the transformations are incomplete or imperfect. The latter for this reason are often classified as a separate order. The _Trichoptera_ are also placed by some entomologists in a distinct order, on account of the peculiarity in their wings being clothed with hairs. They, however, present so many points both in habits and structure, analogous with the true _Neuroptera_, that we have retained them as a sub-division of the Order. TABULAR VIEW OF THE PRINCIPAL FAMILIES OF THE NEUROPTERA. _Sub-Order 1.--Planipennia._ Family 1. Myrmeleontidæ or Ant Lions. Family 2. Hemerobiidæ or Lacewing Flies. Family 3. Mantispidæ or Mantis Flies. Family 4. Sialidæ or Sialis Flies. Family 5. Raphiidæ or Snake Flies. Family 6. Panorpidæ or Scorpion Flies. _Sub-Order 2.--Trichoptera_ (or Caddis Flies). Family 1. Inæquipalpia or Large Caddis Flies. Sub-family 1. Phryganeidæ. Sub-family 2. Limnophilidæ. Sub-family 3. Sericostomidæ. Family 2. Æquipalpia or Little Caddis Flies. Sub-family 1. Leptoceridæ. Sub-family 2. Hydropsychidæ. Sub-family 3. Rhyacophilidæ. Sub-family 4. Hydroptilidæ. _Sub-Order 3.--Pseudo-Neuroptera._ TRIBE I.--ORNOPTERA (or Dragon Flies). Family 1. Libellulinæ or Great Dragon Flies.