386' SYSTEM OF INSECTS. 
Leay; who, however, with his usual accuracy and judg- 
ment, has restored the aspirate to the latter name\ Their 
agreement in having a promuscis, or instrument of suc- 
tion, with a jointed sheath, at present induces me to hesi- 
tate as to the propriety of their separation, and to consi- 
der them as forming secondary rather than primary sec- 
tions of the Class. That you may be enabled to judge 
for yourself upon this subject, I will state the principal 
features in which they differ. In the first place, the He- 
teropterous section usually sucks the juices of animals, 
and the Homopterous, those of plants; in the former, the 
Hemelytra, besides their different substance, as well as 
the wings, cross each other; while in the latter, the organs 
of flight are deflexed, and do not lap over each other at 
all. The antennas also of the one are often long, and do 
not terminate in a bristle ; while in the other, with few 
exceptions, they are very short and setigerous. In the 
Heteroptera the body is depressed and flat, in the Homo- 
ptera convex and thick. In the former, the scutellum is 
one of the principal features of the trunk ; in the latter, 
not at all remarkable b . Other differences in the struc- 
ture, both of head, trunk, and abdomen, might be pointed 
out ; but these you will chiefly find noticed in my letters 
on the External Anatomy of Insects, where I treated of 
those parts. I shall here, therefore, only further men- 
tion the ovipositor also as forming a most striking dis- 
tinction c . 
Def. Metamorphosis semicomplete in almost all. 
Month promuscidate d . 
a Hor. Entomolog. 374—. b Vol. III. p. 554. 
c See above, p. 159 — . 
11 Vol. HI. p. 463. 
