508 EXTERNAL ANATOMY OF INSECTS. 
distinguish the Zarva only of the kindred genus Hemero- 
bius*. These organs differ little in shape, being usually 
perfectly sound and somewhat convex ; but occasionally 
they vary in this respect. In Fulgora serrata they are 
oblong, with a longitudinal depression; in #. Diadema 
they are also umbilicated, but the wmbzlicus is circular ; 
in Corydalis they are oval; in other insects they are 
ovate ; in some semicircular, and in a few triangular. 
They vary much in szze: in some of these animals being 
so minute as to be scarcely visible, while in others, as 
Corydalis, Dorylus, Vespa pallida, Reduvius, &c.*, they 
are as large as some compound eyes. ‘They differ also 
in colour, though often black: in Fulgora laternaria 
they are of a beautiful yellow ; in F. candelaria they are 
white ; in many Hymenoptera they are crystalline, in 
others red: the fierce look of Reduvius personatus is ren- 
dered more hateful by its stemmata having a pale iris 
round a dark pupil®. 
Let us here stop and adore the goodness of a benefi- 
cent Crearor, who, though he has deprived these little 
beings of the moveable eyes with which he has gifted the 
higher animals, has made it up to them by the variety 
and complex structure of their organs of vision, where 
we have only ¢wo points of sight, giving ¢hem more than 
as many myriads. 
5. Antenna.—But of all the organs of insects, none 
appear to be of more importance to them than their An- 
denne, and none certainly are more wonderful and more 
various in their structure, and probably uses. Upon 
a De Geer iii. ¢. xxvii. f. 1. Reaum, iii. ¢, xxxii. f. 3, 9. 
» Pirate XXVI. Fic. 40. 
