The males are very small, free-flying insects with the prothorax, mesothorax and elytra greatly reduced, the latter appearing as little, twisted strips, while the metathorax is relatively large, with its wings broad and capable of longitudinal folding.
These firm fore-wings, or elytra (fig.
The identification of the elytra of beetles with the fore-wings of other insects has indeed been questioned (1880) by F.
The tergite of the prothorax (pronotum) is prominent in all beetles, reaching back to the bases of the elytra and forming a substantial shield for the front part of the body.
It is true that in beetles and certain other insects there are the elytra or wing cases - thin, light, horny structures inclined FIG.
Of cantharidin has been obtained from different samples; and it has been ascertained that the elytra or wing-sheaths of the insect, which alone are used in pharmacy, contain more of the active principle than the soft parts taken together; but apparently cantharidin is most abundant in the eggs and generative organs.
The prothorax is convex in front, and is usually drawn out behind into a prominent process on either side, while the elytra are elongate and tapering.
The elytra are very hard, and in some cases fused with one another, rendering flight impossible.
The pronotum and elytra are often adorned with bright colours or metallic lustre, and marked with stripes or spots.
In many beetles the hindwings are reduced to mere vestiges useless for flight, or are altogether absent, and in such cases the two elytra are often fused together at the suture; thus organs originally intended for flight have been transformed into an armour-like covering for the beetle's hind-body.