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CHAPTER IV. 



ORGANS AND CHARACTERS OF VARIATION. 



Having in the preceding chapter briefly alluded to 

 some of the principal causes by which the outward 

 aspect of the insect tribes would seem to be in a large 

 measure (though within definite specific limits) regu- 

 lated, it may perhaps be desirable to gather into a 

 small compass, from those remarks, what the chief 

 organs and characters are which appear to be more 

 peculiarly beneath the control of the various influences 

 which we have been just discussing. To imagine that 

 when an insect has become much altered in its general 

 contour, all the parts of which it is composed are 

 equally affected, is contrary to experience ; since obser- 

 vation warns us that there are but few actual members 

 which are capable of change, — whilst even the external 

 features, or secondary diagnostics, are only interfered 

 with according to a fixed law, the workings of which are 

 necessarily modified, in proportion as the constitutions 

 of the several animals are diflFerently organized and 

 acted upon. 



As regards positive structure, indeed, we can have 

 but few observations to communicate, — seeing that the 

 limbs and appendages themselves are usually of so con- 



