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has been seen by the brief synoptical view given on a former page, this order is essentially characterised by a mouth organised for gnawing, and four naked membranous wings of equal consistency—that is, the superior pair are not thickened for the purpose of protecting the others, as is the case with the orders hitherto described. To these must be added, in order to render the definition exclusive of some of the following orders, that the wings are reticulated or interlaced with a delicate net-work—a character indicated by the name, which is derived from, a nerve, with the ordinary postfix. All the wings are fully fitted for flight, and in the majority of cases both pairs are of equal size, as we see them in dragon-flies. But in some tribes the posterior pair are smaller than the others, (in this respect resembling the Hymenoptera,) and in a few cases they entirely disappear. The reticulations are finer and denser in some than in others, but they are always too numerous, variable, and minute to be available for the purposes of classification, like the cells of the Hymenoptera. When at rest their position is various, but most commonly they are extended at right angles from the body, nearly in the same manner as they are borne during flight. In other cases, the upper pair are incumbent on the lower, and deflexed at the sides. It might at once be inferred