116 INTRODUCTION TO 



our relief ; and solves the difficulty by affirming that 

 membranous wings are desiccated branchiae ana- 

 logous to the branchiae of fishes ; and, moreover, that 

 elytra are the analogues of the shells of bivalve 

 mollusca ! ! Mr. Kirby is disposed to consider them 

 as having some relation to the membranous expan- 

 sions found in certain Saurian reptiles of the genus 

 Draco ; but wisely refrains from doing more than 

 merely throwing out the hint that such may be the 

 case. It is surely more natural to regard them with 

 M. Audouin, as organs sui generis, destined to exer- 

 cise a particular function, and undergoing such modi- 

 fications as best adapt them for fulfilling that function 

 in every variety of circumstances.* 



As the wings occupy the superior portion of the 

 thorax, and serve for aerial motion, so the legs are 

 appropriated to the lower, and furnish the means of 

 moving on the earth and in the water. Their num- 

 ber never exceeds or falls short of six ; this rule 

 being so invariable, that any articulated animal found 

 not to conform with it, may at once be concluded 

 not to belong to the class. Their position has been 

 already indicated ; a pair being appropriated to each 

 of the three principal divisions of the thorax, and 

 their distance from each other at the points of in- 

 sertion depends on the greater or less extension of 

 these divisions on their inferior or sternal face. They 

 are distinguished as the fore, middle, and hind legs. 



The joint which unites the leg with the body is 



* See Lacord. Intro, a 1' Entom. I. 409. 



