72 EVENINGS AT THE MICROSCOPE. 



right, to the left, and in all directions, that this bird of 

 rapid flight and ready evolution was unable to overtake 

 and capture it, the insect eluding every attempt, and being 

 in general fully six feet in advance of the bird. A Dragon- 

 fly has been known to fly on board a ship at sea, the 

 nearest land being the coast of Africa, five hundred miles 

 distant, a fact highly illustrative of its power of wing. 



It is a point of interest to know the structure of the 

 organs by which such results are accomplished, and there- 

 fore we will devote an hour to the microscopical examina- 

 tion of the wings of one or two insects. Let us begin 

 with the common Fly, one of which, a fine blue-bottle, is 

 somewhat noisily buzzing in the window ; — 



" The blue-fly sung i' the pane/' — 



as if to invite our attention to him. Well, we will 

 borrow one of his wings for the lesson ; and, putting it 

 into the stage-forceps, we shall be able to turn it in any 

 direction for observation beneath the microscope. 



At first it seems a very thin transparent membrane, of 

 a shape between triangular and oval, with a few fine 

 black lines running through it, and along one edge. But 

 on bringing a greater magnifying power to bear on it, we 

 see that the clear surface is covered with minute short 

 stiff hairs, each of which has an expanded base. And 

 still further, by delicate focussing, we find that there are 

 two sets of these hairs, which come into view alternately, 

 those of one row projecting upward towards our eye, 

 those of the other downward. They are placed on both 

 the upper and under surfaces, and are in fact appendages 

 of two distinct membranes, applied to each other. There 

 is some reason to believe that these hairs are delicate 

 organs of touch, communicating impressions through the 

 skin to a sensitive layer beneath ; at least such seems 

 their function on the body, and we may judge from 

 analogy that it is not different here. 



