288 
SYSTEMATIC ARRANGEMENT. 
from examining the wing of a dragon-fly, that this is 
one of 4he orders iti which flight attains its maximum 
of power. The insect just named has always been 
celebrated for its easy aud 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 antenme, 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 PI. XXVI. 
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 7, 7, 
the occiput, reduced to a minute size by the enlarged size 
of the eyes, c, c ; 0, the ocelli *, a, a , the antennoi ; 6, a tu- 
bercle enclosed between the eyes and ocelli ; c and e', the 
face, divided into two parts, (the nasus and postnasus of 
Kirby, Intr. PI. 6, p. 10, a, b ;) d, the clypeus, (Rhenarium, 
