CHAPTER XVII. 



INSECTS AND ARACHNIDA. 



Theee is no class in the whole Animal Kingdom which affords 

 to the Microscopist such a wonderful variety of interesting 

 objects, and such facilities for obtaining an almost endless suc- 

 cession of novelties, as that of Insects. For, in the first place, 

 the number of different kinds that may be brought together (at 

 the proper time) with extremely little trouble, far surpasses that 

 which any other group of Animals can supply to the most pains- 

 taking collector ; then, again, each specimen will afford, to him 

 who knows how to employ his materials, a considerable number 

 of microscopic objects of very different kinds ; and, thirdly, 

 although some of these objects require much care and dexterity 

 in their preparation, a large proportion may be got out, examined, 

 and mounted, with very little skill or trouble. Take, for exam- 

 ple, the common House-Fly: — its eyes maybe easily mounted, 

 one as a transparent, the other as an opaque object (§ 383) ; its 

 antennae, although not such beautiful objects as those of many 

 other Diptera, are still well worth examination (§ 385) ; its 

 tongue or " proboscis" is a peculiarly interesting object (§ 386), 

 though requiring some care in its preparation ; its spiracles, 

 which may be easily cut out from the sides of its body, have a 

 very curious structure (§ 392) ; its alimentary canal affords a 

 very good example of the minute distribution of the "tracheae" 

 (§ 391) ; its wings, examined on a living specimen, newly come 

 forth from the pupa state, exhibit the circulation of the blood in 

 the " nervures" (§ 390) ; the wing of the insect when dead, 

 moreover, exhibits a most beautiful play of iridescent colors, 

 and shows a remarkable areolation of surface, when it is exa- 

 mined by light reflected from its surface at a particular angle 

 (§ 395) ; it&foot has a very peculiar conformation, which is doubt- 

 less connected with its singular power of walking over smooth 

 surfaces in direct opposition to the force of gravity, although the 

 mode in which it serves this purpose is not yet _ certainly ascer- 

 tained (§ 897) ; and the structure and physiology of its sexual 

 apparatus, with the history of its development and metamor- 

 phoses, would of itself suffice to occupy the whole time of an 



