74 



EVENINGS AT THE MICROSCOPE. 



seeming to be, as it were, cut out of the hinder and inner 

 side of the fore ones. The two edges the hinder edge of 



the fore pair and the 

 front edge of the hind 

 pair then corre- 

 spond, but it is neces- 

 sary that, during flight, 

 when the wings are ex- 

 panded, the two wings 

 on each side should 

 maintain this relative 

 position, neither over- 



.- ^ ^ - ^~ . - , lapping the other, but 

 ' together presenting 



DOUBLING AND HOOKS IN A BEE<S WING. ^ ^^ g^fo^ 



wherewith to beat the 



air. There must be, therefore, some contrivance for lock- 

 ing together the two edges in question, which yet shall 

 be capable of being unlocked at the pleasure of the 

 animal ; for the wings during repose slide over one 

 another. This contrivance is furnished by a series of 

 hairs or spines running along the front edge of the hind- 

 wing; they are bent up into strong semicircular hooks, 

 arching outwards, looking, under a high power, like the 

 hooks on a butcher's stall. On the other hand, the margin 

 of the fore-wing is strengthened, and is turned over with 

 a shallow doubling, so as to make a groove into which the 

 hooks catch ; and thus, while the fore- wings are expanded, 

 the hooks of the other pair are firmly locked in their 

 doubled edge, while, as soon as flight ceases, and the 

 wings are relaxed, there is no hindrance to the sliding of 

 the front over the hind pair. 



The wings of many insects are interesting on account of 

 the organs with which they are clothed. A familiar ex- 

 ample is furnished by the common Gnat, a wing of which 

 is on the slide now before us. There is the same general 



