from examining the wing of a dragon-fly, that this is one of the orders in which flight attains its maximum of power. The insect just named has always been celebrated for its easy and rapid evolutions, and like a few other kinds, it is able to dart backwards or sidewise with equal ease.
The head is frequently of large size, and in the species most strongly characteristic of the order, the greater portion of it is occupied by the composite eyes, which are unusually developed in harmony with their predacious habits. The ocelli, when present, (which is commonly the case,) are placed on the forehead, and are often very conspicuous. Such, however, is not generally the case with the antennæ, as they are short, subulate, and slender, in one principal division of the order; but in the other, they are longer and occasionally very prominent.
The trophian strictly of a masticating kind, and in not a few instances, exactly like those of the Orthoptera. Their appearance in Libellula is accurately exhibited on Pl. XXVII.
Figures 1-10 comprise details of the head of the common dragon-fly, Libellula depressa (fem.) The first five figures represent the head in different positions; the same letters are, throughout, applied to the same parts.—Figure 1, the head seen from above, fig. 2, from beneath, fig. 3. in front, fig. 4, from behind, fig. 5, laterally; p, the vertex, and q, q, the occiput, reduced to a minute size by the enlarged size of the eyes, e, e; o, the ocelli; a, a, the antennæ; b, a tubercle enclosed between the eyes and ocelli; c and c′, the face, divided into two parts, (the nasus and postnasus of Kirby, Intr. Pl. 6, p. 10, a, b;) d, the clypeus, (Rhenarium,
