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The elytra.

Fig. 139.—Longitudinal section through the edge of the elytrum of Lina ænea: gl, glands; r, reservoir; fb, fat-body; m, matrix; u, upper,—l, lower, lamella.—After Hoffbauer.

Hoffbauer finds that in the elytra of beetles of different families the venation characteristic of the hind wings is wanting, the main tracheæ being irregular or arranged in closely parallel longitudinal lines, and nerve-fibres pass along near them, sense-organs being also present. The fat-bodies in the cavity of the elytra, which is lined with a matrix layer, besides nerves, tracheæ, and blood, contain secretory vesicles filled with uric-acid concretions such as occur in the fat-body of Lampyris. There are also a great many glands varying much in structure and position, such occurring also in the pronotum (Fig. 139).

Meinert considers the elytra of Coleoptera to be the homologues of the tegulæ of Lepidoptera and of Hymenoptera. He also calls attention to the alula observed in Dyticus, situated at the base of the elytra, but which is totally covered by the latter. The alulæ of these beetles he regards as the homologues of the anterior wings of Hymenoptera and Diptera. No details are given in support of these views. (Ent. Tidskrift, i, 1880, p. 168.)