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CHAPTER XXI 



INSECTS AND ARACHNID A 



THERE 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 succession 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 ex- 

 tremely little trouble far surpasses that which any other group of 

 animals can supply to the most painstaking 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 example, the common house-fly ; its eyes may 

 be easily mounted, one as a transparent, the other as an opaque 

 object ; its antennae, although not such beautiful objects as those of 

 many other Diptera, are still well worth examination ; its tongue or 

 'proboscis' is a peculiarly interesting object, 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; its 

 alimentary canal affords a very good example of the minute distri- 

 bution of the trachea! ; its wing, examined in a living specimen 

 newly come forth from the pupa state, exhibits the circulation of 

 the blood in the ' nervures,' and when dead shows a most beautiful 

 play of iridescent colours, and a remarkable ar eolation of surface, 

 when examined by light reflected from its surface at a particular 

 angle ; its foot has a very peculiar conformation, which is doubtless 

 connected with its singular power of walking over smooth surfaces 

 in direct opposition to the force of gravity, while the structure 

 and physiology of its sexual apparatus, with the history of its develop- 

 ment and metamorphoses, would of itself suffice to occupy the whole 

 time of an observer who should desire thoroughly to work it out, not 

 only for months, but for years. 1 Hence, in treating of this department 

 in such a work as the present, the Author labours under the embarras 

 des richesses ; for, to enter into such a description of the parts of the 

 structure of insects most interesting to the microscopist as should 



1 See Mr. Lowne's valuable treatise on The Anatomy and Physiology of the 

 Blow-fly, 1870 ; second edition 1891-4. 



