288 SYSTEMATIC ARRANGEMENT. 



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 fore- 

 head, and are often very conspicuous. Such, how- 

 ever, is' not generally the case with the antennae, 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 trophi are strictly of a masticating kind, and in 

 not a few instances, exactly like those of the Orthop- 

 tera. Their appearance in Libellula is accurately 

 exhibited on PL XXVI. 



Figures 1-10 comprise details of the head of the common 

 dragon-fly, Libellula depressa (fern.) 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 ; />, the vertex, and 7, 7, 

 the occiput, reduced to a minute size by the enlarged size 

 of the eyes, e, e ; o, the ocelli ; a, a, the antenna? ; 6, a tu- 

 jbercle 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, 



