INSECTA. 



in which lie was an eye-witness of the comparative capabilities of 

 the Dragon-fly and the Swallow, as relates to the perfection of their 

 flight. The bird and the insect were both confined in a mena- 

 gerie about a hundred feet long, and apparently their powers were 

 fairly tested. The swallow was in full pursuit, but the little crea- 

 ture flew with such astonishing velocity, that this bird of rapid 

 flight and ready evolution was unable to overtake and entrap it ; 

 the insect eluding every attempt, and being generally six feet 

 before it. " Indeed," say the authors from whom we quote 

 the above anecdote,* " such is the power of the long wings by 

 which the dragon-flies are distinguished, and such the force of the 

 muscles which move them, that they seem never to be wearied with 

 flying. I have observed one of them (Anax Imperator, Leach) 

 sailing for hours over a piece of water, sometimes to and fro, and 

 sometimes wheeling from side to side, and all the while chasing, 

 capturing, and devouring the various insects that came athwart its 

 course, or driving away its competitors, without ever seeming 

 tired or inclined to alight." 



In Hymenopterous insects (Jigs. 128 and 129), the wings are 

 much more feebly organized, but their structure is similar ; the 

 nervures, or horny ribs, supporting the membranous expansion, 

 are comparatively few, and in the Diptera they are still less nu- 

 merous. 



In several orders the anterior pair of wings are converted into 

 shields for the protection of the posterior ; such is the case in the 

 Orthoptera, many of the Hemiptera, and more especially in the 

 Coleopterous genera. In the latter, indeed, they are very dense 

 and hard ; and, being nearly unserviceable in flight, the hinder pair 

 are necessarily developed to such a size as to present a very ex- 

 tensive surface (fig. 106, A), and when in repose are closely 

 folded up beneath the elytra, and thus carefully preserved from 

 injuries to which they would be constantly exposed without such 

 provision for their security. 



(289.) The above observations relate only to the general disposi- 

 tion and connection of the different parts of the skeleton, and loco- 

 motive appendages connected with it; it remains for us now to speak 

 more fully of the texture of the external integument, and those 

 modifications which it presents, adapting it to various purposes. 



The hard covering of an insect, like the skin of vertebrate 

 animals, consists of three distinct layers. The outer stratum or 



* Kuby and Spence, op. cit. p. 351. 



