6 INTEODUCTION. 



ill-developed or absent this shoulder is not developed, and the 

 sides of the pronotum form a continuous line with those of the 

 elytra. In normally winged forms the axillary portion of the elytra 

 is as a rule rectangular, so that in repose the sutural margins are 

 in contact from base to apex ; but in feebly winged or apterous 

 forms the axillary angle may be rounded, so that a small portion 

 of the mesonotum is exposed at the base of the suture, even when 

 these organs are in repose : this portion of the mesonotum is in 

 such cases hardened by exposure, and is termed the scutellum. 

 As a rule, in fully Avinged forms the pronotum extends backwards 

 over the base of the elytra and prevents the exposure of any 

 scutellum ; but in Apaehijus, Diplatys, and the Pygldicranince the 

 axillary augle is rounded off so that the elytra are oval rather than 

 rectangular, and at the same time the pronotum is not produced 

 backwards and cousequeutly the scutellum is prominent. The 

 disc of the elytra is always fiat, and it is the disc which is implied 

 when the ehjtra is used in description without qualification. The 

 small vertical costal area is sometimes of a different colour. The 

 elytra may be rectangular and so parallel in repose, as is usually 

 the case, or they may be dilated and convex, broad at the shoulders 

 and narrowing posteriorly as in Hi/jnirgus, Pterijf/iila, andiAUodahlia. 

 In Apacliyus and Diplatys the distinction between the disc and 

 costal area is weak and the whole elytra lie flat upon the thor'ax. 

 The apex of the elytra is truncate in hemiapterous forms, generally 

 sinuate in winged forms, or obliquely truncate. 



When rudimentary, the elytra are very much shortened ; they 

 may be mere lateral flaps on the sides of the mesonotum (BorelUa), 

 or they may still be sufficiently large to meet at the median suture 

 in the apical portion (Obelura, Lijjcirura) ; the weakening of the 

 axillary augle and consequent exposure of a scutellum is the first 

 step towards abbreviation. The elytra may be perfectly smooth 

 {Forficida, &c.), or granulose (AUodaJdia), or clad with short, 

 obtuse bristles (Echimsoma), or punctulate (certain species of 

 Forcipida). 



The 7iind wlnqs are often entirely absent (Anisolahis and 

 Brachylabince) ; when perfectly developed (which is the rule) they 

 are semicircular in shape, very ample and membranous ; the basal 

 half of the costal margin is hardened into a leathery scale which 

 protrudes from beneath the elytra in repose, and it is this scale 

 \\'hich is meant when the word " wing " is used without quahfica- 

 tion. From the apex of this scale the wing-veins radiate, and 

 when the wings are closed they shut up fanwise about this point ; 

 they are then folded transversely at right angles to the first line of 

 folding and so tucked away under the scale that they are entirely 

 hidden when in repose. In Apachyus and Diplatys, however, the 

 membranous folds are visible along the suture during repose. The 

 basal margins of the squamce, or hardened scales, are in contact 

 M-hen in repose, and thus form the continuation of the suture 

 of the elytra. The wings are frequently abbreviated, and it is 



