EXTERNAL ANATOMY OF INSECTS. 595 



dium, &c. ; hemelytra in the bed-bug a ; ivings in many 

 female moths, in Cryptus hemipterus a Hymenopterous 

 insect, &c. 



iii. Composition. The structure of wings has been 

 before explained to you b , and I shall again have occa- 

 sion to allude to it; but here I wish to call your attention 

 to a circumstance that has not hitherto, that I recollect, 

 been adverted to ; I mean that all kinds of organs of 

 flight, and it may be traced as we shall soon see even in 

 elytra, are divided longitudinally into three areas or folds; 

 the first or external one I call the Costal Area G from its 

 beginning with the costal nervure ; the second is the In- 

 termediate Area d ; and the third is the Anal Area e . 



Having made these observations with respect to the 

 organs of flight in general, I shall now proceed to consider 

 more at large the elytra, tegmina, hemelytra, and "wings. 



i. Elytra. These are the wing- covers of the Coleoptera 

 Order, distinguished from tegmina by the absence of 

 nervures, from hemelytra by the want of the membrane 

 at the apex, and from both by their uniting in almost 

 every instance at the suture. I shall consider them as 

 to their substance ,• articulation with the trunk; expan- 

 sion; parts; shape-, appendages; sculpture; clothing; 

 colours, and uses. 



1. Substance. The firmness of the substance of elytra 

 is usually regulated by that of the crust of the insect to 

 which they belong ; in hard insects they are hard, and 



3 De Geer, iii. t. xvii./. 10, 11.//. M. Savigny has noticed a part 

 in some Annelides, which he regards as analogous to elytra. Systeme 

 des Annelides, 4, 9, 1 1. b Vol. II. p. 346—. 



c Plates X. and XXVIII. b: d Ibid. c. e Ibid, d: 



2 O 2 



