386 SYSTEM OF INSECTS. 



Leay ; who, however, with his usual accuracy and judg- 

 ment, has restored the aspirate to the latter name a . 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. Tht 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 antennae 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. 

 Mouth promuscidate d . 



3 Hor. Entomolog. 374. b VOL. III. p. 554. 



c See above, p. 159. 

 " VOL. III. p, 463. 



