Wings covered by Hemelytra or Tegmina[1209].
Tarsi mostly trimerous, rarely dimerous or monomerous[1210].
8. Trichoptera[1211] Kirby (Synistata F. Neuroptera Latr.). MM. Latreille and MacLeay are of opinion that Semblis F. and Phryganea L. ought to be associated in the same group; and the latter gentleman has backed his opinion by some apparently cogent arguments[1212]: there are others, however, that seem to me more cogent, for considering them as belonging to different Orders. Whoever examines the several tribes into which Mr. MacLeay has divided the Neuroptera, will observe in all of them a distinct prothorax, a circumstance which they possess in common with those Orders that use their mandibles for mastication; whereas in those that do not use them for mastication, as the Hymenoptera, or that take their food by suction, this part is replaced by a mostly narrow collar, forming a part of the alitrunk[1213]. The existence then of the prothorax in the Perlidæ, and of the collar in the Trichoptera, affords no slight presumptive evidence that they belong to different Orders. Another circumstance that weighs much with me is, that the type of the neuration of the wings in Perla is taken from the Neuroptera, in the Trichoptera from the Lepidoptera; the same observation extends to the legs of both[1214], and likewise to the abdomen. Even in their oral organs, as far at least as relates to their mandibles, those of Perla, though membranaceous—a circumstance occurring even in Coleoptera—are of a Neuropterous type; while the angular termination of the cheeks in the Phryganeæ approaches to the Lepidopterous mandibular rudiments. The principal argument on which Mr. MacLeay's opinion seems to rest, is, that the larvæ of both are aquatic, and clothe themselves in cases formed of various materials: but though this circumstance shows that they approximate in the system, it does not prove that they belong to the same order, since the general habit and appearance of the two animals when arrived at perfection contravenes it. The larvæ of Myrmeleon and of Leptis Vermileo form pitfalls of sand for their prey, and when they become pupæ, cover themselves with it[1215]; but this in them does not even prove an affinity, but only an analogy. The larva of Perla is carnivorous[1216], that of Phryganea mostly herbivorous[1217]: so that they are not precisely similar in their habits. Whether they resemble each other altogether, in their form, does not clearly appear. The above reasons will, I trust, justify me for considering them at present as belonging to different Orders; but if further discoveries should confirm the opinion Mr. MacLeay espouses, I shall have no hesitation in yielding to it.
Def. Metamorphosis incomplete[1218].
Mouth emandibulate.
Prothorax replaced by a collar.
Wings four, upper pair mostly hairy, lower ample, folded: neuration branching.
Anus without setæ. Eggs extruded in a gelatinous mass[1219].
9. Lepidoptera[1220] (Glossata F.). Concerning this Order, no difference of opinion exists amongst Entomologists. Besides the scales that cover their wings, they are distinguished by the peculiar instrument of suction formerly described: neither of these characters, however, is perfectly universal; some of the Order (Nudaria) having no scales upon their wings, and others being without any antlia (Aglossa). Other peculiar characters are to be found in them; for instance, the patagia, or tippets, that adorn their evanescent thorax[1221], and the tegulæ, or base-covers, of a shape quite dissimilar to those of Hymenoptera, which cover and defend the base of their wings[1222]. As in the last Order, their legs are located all together with scarcely any space intervening between them; and they often agree also in their spurs.