2G ELEMENTS OF EXTOMOI.OGY. 



clearly exemplified in that description of wings which is usually term- 

 ed transparent, as in the common house-tty and the bee. The true 

 wing, by means of which the insect is enabled to fly, is always con- 

 structed in tliis manner, whatever may be its appearance externally, 

 arising from a superficial covering of down, feathers, hair, or any other 

 cause. Tlie variety in the form and structure of the wings, in the 

 number, figure, and disposition of the nervures, or the colours with which 

 they are adorned, is infinite. The diversity in the disposition of the 

 nervure is evident from a comparison of the simply constructed wing ot 

 the common house-fly witli the complex wing of the Fanorpa or the 

 Ephemera, or the wings of an earwig, which consists of a series of sin- 

 gle nervure, with the elaborately wrought lattice-work of the wing of the 

 LibcUula. The whole of the Icpidopterous order exhibit the superficial 

 coating of feathers, down, or hairs; and upon the removal of these the 

 wings are found constructed in the same manner as the transparent 

 wings of the other orders. A variation in the form of the wing as well 

 as its texture is manifest throughout all insects of the winged kind. 

 Those of tlie Cokoptera have two n\cmbranaceous wings, wliich fold 

 upon each other, forming a plait or double at their external margin, 

 which fold is accommodated by a peculiar joint in the main rib ot 

 the wing, and the disposition of the nerxaires in the middle of the whig 

 contiguous. In the Hcmiplcra the wings generally fold longitudinally, 

 without any transverse double ; so that in expansion these parts open 

 somewhat like a fan. The anterior wings of the Lepidopiera are neither 

 doubled aci'oss nor folded longitudinally; they are entirely llat, and 

 are but little capable of contraction and dilatation. In the genus Pa- 

 pilio they are endowed with the power of erection, which is rarely the 

 case in the Phalaua:, though occasionally observed among the Sphin- 

 ges; the Pha/ana have the lower wings concealed under the anterior 

 pair, the latter being laid in a flat position over them. The wings of 

 tlie Lepidopfera are downy, and often decorated with very beautiful 

 colours disposed in the most pleasing and varied manner. The Ke}4- 

 roptera in general have the wings flat; this is not invariable; they are 

 constantly membranaceous, and reticulated with nervures. In the 

 Hymenoptera the wings are membranaceous, generally flat, but some- 

 times folded when the insect settles, as in the wasp genus. The Dipte^ 

 rous order cannot be confoimded with the preceding, as they have only 

 two wings : they are membranaceous as in the former. 



In all insects of the winged kind these organs present the greatest 

 diversity, and aftbrd characters both for genera and species less liable 

 tf> fluctuation than common observers would conceive. The numl)cr, 

 figure, construction, proportion, consistence, and texture of the wings 

 have enabled natiu'alists to distribute insects into principal groups 

 with considerable precision. Linne derived nmch assistance from an 



