WINGS AND ELYTRA OF INSECTS. 575 



best displays its most interesting features, it should be set up as 

 nearly as possible in the same. For this purpose it should be 

 mounted on an opaque slide ; but instead of being laid down 

 upon its surface, the wing should be raised a little above it, its 

 " stalk" being held in the proper position by a little cone of soft 

 wax, in the apex of which it may be imbedded. The wings of 

 most Hymenoptera are remarkable for the peculiar apparatus by 

 which those of the same side are connected together, so as to 

 constitute in flight but one large wing ; this consists of a row ot 

 cuiTed hooks on the anterior margin of the posterior wing, 

 which lay hold of the thickened and doubled-down posterior 

 edge of the anterior wing. These hooks are sufficiently appa- 

 rent in the wings of the common Bee, when examined with even 

 a low magnifying power ; but they are seen better in the Wasp, 

 and better still in \he' Hornet. The peculiar scaly covering of the 

 wings of the Lepidoptera has already been noticed (§ 381) ; but 

 it may here be added that the entire wings of many of the 

 smaller and commoner insects of this order, such as the Tineidce 

 or "clothes' moths," form very beautiful opaque objects for low 

 powers; the most beautiful of all being the divided wings of the 

 Fissipennes or "plumed moths," especially those of the genus 

 Pterophorus. 



396. There are many Insects, however, in which the wings are 

 more or less consolidated by the interposition of a layer of horny 

 substance between the two layers of membrane. This plan of 

 structure is most fully carried out in the Coleoptera (beetles), in 

 which the anterior wings are so much thickened and are so little 

 extended, that they are useless in flight, and serve merely as 

 cases or covers for the posterior, which lie folded up beneath 

 them when not in use ; hence these are distinguished as elytra. 

 These elytra, when the insect is at rest, meet along the median 

 line of the back, and cover nearly the whole upper surface of the 

 body ; and it is upon them that the brilliant hues, by which the 

 integument of many of these insects is distinguished, are most 

 strikingly displayed. In the anterior wings of the Forficulidoe or 

 earwig tribe (which foi-m the connecting link between this order 

 and the Orthoptera), the cellular structure may often be readily 

 distinguished when they are viewed by transmitted light, espe- 

 cially after having been mounted in Canada balsam. The ante- 

 rior wings of the Orthoptera (grasshoppers, crickets, &c.) although 

 not by any means so solidified as those of Coleoptera, contain a 

 great deal of horny matter ; they are usually rendered sufficiently 

 transparent, however, by Canada balsam, to be viewed with 

 transmitted light; and many of them are so colored as to be very 

 showy objects (as are also the posterior fan-like wings) for the 

 solar or gas-microscope, although their large size, and the ab- 

 sence of any minute structure, prevent them from affording much 

 interest to the ordinary Microscopist. We must not omit to 

 mention, however, the curious sound-producing apparatus which 



