678 WINGS OF INSECTS. 



that the veins, after subdividing, reunite again, so as to form a 

 close network ; whilst in the Hymenoptera and Diptera such re- 

 unions are rare, especially towards the margin of the wings, and 

 the areola? are much larger. Although the membrane of which 

 these Wings are composed appears perfectly homogeneous when 

 viewed by transmitted light, even with a high magnifying power, 

 yet, when viewed by light reflected obliquely from their surfaces, 

 an appearance of Cellular areolation is often discernible ; this is 

 well seen in the common Fly, in which each of these areolae has a 

 hair in its centre. In order to make this observation, as well as 

 to bring-out the very beautiful Iridescent hues which the Wings of 

 many minute Insects (as the Aphides) exhibit when thus viewed, 

 it is convenient to hold the Wing in the Stage-Forceps for the sake 

 of giving it every variety of inclination; and when that position 

 has been found which best displays its most interesting features, it 

 should be set up as nearly as possible in the same. For this pur- 

 pose 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 of curved Hooklets on the anterior margin of the posterior 

 wing, which lay hold of the thickened and doubled-down posterior 

 edge of the anterior wing. These hooklets are sufficiently apparent 

 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 the Hornet. —The peculiar Scaly covering of the 

 Wings of the Lepidoptera has already been noticed (§ 512) ; 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 

 Pterojihorus. 



529. 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), whose 

 anterior wings are metamorphosed into Elytra or Wing-cases ; and 

 it is upon these that the brilliant hues by which the integument 

 of many of these Insects is distinguished, are most strikingly dis- 

 played. In the Anterior Wings of the Forficulida or Earwig- 

 tribe (which form the connecting link between this Order and the 

 Orthoptera), the Cellular structure may often be readily distin- 

 guished when they are viewed by transmitted light, especially 

 after having been mounted in Canada Balsam. The Anteiior 



