MOTIONS OF INSECTS. 363 



it vibrated its wings as much by candle-light as in 

 the sunshine, probably from the habit of associating 

 the two movements, yet, whenever it remained sta- 

 tionary, it kept the wings motionless. Had the 

 motion been indispensable to respiration, and analo 

 gous to the motion of the gills of fish, or the panting 

 in the anal scale of the water-louse {Asellus aqua- 

 ticus, Leach), this cessation would not have taken 

 place at night. 



We are, therefore, perhaps justified in concluding 

 that the vibration of the wings in this little fly is an 

 indication of being pleased; in the same way as 

 a nestling sparrow, when fed by its dam, will half 

 stretch its wings, and, as Thomson finely expresses 

 it, will 



" Quiver every feather with desire ;" 



or as a lamb when sucking will vibrate its tail, as 

 well as the pretty birds popularly termed wagtails 

 (MotacillcB), when they perambulate the margm of 

 a stream and find a plentiful banquet of insects to 

 their liking. 



It may prove still more interesting, we think, to 

 turn our attention to some other movements of in- 

 sects which seem to be expressive of pleasure when 

 they are not stationary, and leaving out of consider- 

 ation, also, their foraging for food. A familiar in- 

 stance of what we allude to occurs in the aerial 

 dances of the tipulidan gnats and some other insects. 

 These are performed not only in summer, but fre- 

 quently even in winter and in the earlier months of 

 spring, — in sheltered places, indeed, such as under 

 trees and hedges, in lanes, and when a day chances 

 to be finer than usual, though the mildest day is of 

 course at these seasons comparatively chill. The 

 most common of these winter dancers is called by 

 Harris the tell-tale (Trichocera hiemalis, Meigen), 



y2 



