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The halteres.

Meinert finds structures in the Lepidoptera which he considers as the homologues of the halteres of Diptera. “In the Noctuidæ,” he remarks, “I find arising from the fourth thoracic segment (segment médiaire), but covered by hair, an organ like the halter of Diptera.” (Ent. Tidskrift., i, 1880, p. 168.) He gives no details.

In the Stylopidæ, on the contrary, the fore wings are reduced to little narrow pads, while the hind wings are of great size.

The thyridium is a whitish spot marking a break in the cubital vein of the fore wing of Trichoptera; these minute thyridia occur in the fore wings of the saw-flies; there is also an intercostal thyridium on the costal part of the wings of Dermaptera.

The fore wings of Orthoptera are thicker than the hinder ones, and serve to protect the hind-body when the wings are folded; they are sometimes called tegmina. It is noteworthy, that, according to Scudder, in all the paleozoic cockroaches the fore wings (tegmina) were as distinctly veined as the hinder pair, “and could not in any sense be called coriaceous.” (Pretertiary Insects of N. A., p. 39.) Scudder also observes that in the paleozoic insects as a rule the fore and hind wings were similar in shape and venation, “heterogeneity making its appearance in mesozoic times.” In the heteropterous Hemiptera, also, the basal half of the fore wings is thick and coriaceous or parchment-like, and also protects the body when they are folded; these wings are called hemelytra. In the Dermaptera the small short fore wings are thickened and elytriform.