MOTIONS OF INSECTS. 363 



wings as much by candle-light as in the sunshine, pro- 

 bably from the habit of associating the two movements, 

 yet, whenever it remained stationary, it kept the wings 

 motionless. Had the motion been indispensable to re- 

 spiration, and analogous to the motion of the gills of 

 fish, or the panting in the anal scale of the water-louse, 

 {Jlsellus aquaticus, 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 Thompson 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 {Mota- 

 cilice), when they perambulate the margin 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 insects 

 which seem to be expressive of pleasure when they are 

 not stationary, and leaving out of consideration, also, 

 their foraging for food. A familiar instance of what 

 we allude t® occurs in the aerial dances of the tipuli- 

 dan gnats and some other insects. These are per- 

 formed not only in summer, but frequently even in 

 winter, and in the early months of spring, — in shelter- 

 ed 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 win- 

 ter dancers is called by Harris the tell-tale (Tricho- 

 cera hiemalisy Meigen), a troop of which may be 

 occasionally seen gamboling in a sunny nook, though 

 the ground be covered with snow. When the weather 



