362 INSECT TRANSFORMATIONS. 



furnishes a good example, putting itself in a constant 

 state of preparation, jerking its piebald head up and 

 down as it skips from stone to stone of the brook, to 

 pounce under water upon the first grub it espies swim- 

 ming. In the same way the red-breast (Sylvia rube- 

 cula) pops jerking about when on the look-out for ca- 

 terpillars; and so habitual does this become, that he 

 does not fail to go through the mano3uvre when he 

 pecks up a crumb at the cottage door, as well as when 

 he pounces upon a caterpillar in the woods, where it is 

 often indispensable to secure the aim to prevent the 

 insect putting in force some stratagem of escape.* 



We may next turn to a small two-winged fly, which, 

 though equally common in gardens and elsewhere with 

 the fanning butterflies (Vanessce) just alluded to, we 

 can scarcely (considering its size) expect to have at- 

 tracted the notice of those who pay little attention to 

 insects. We allude to the vibrating fly ( Seioptera m- 

 brans, KIRBY), which is not above a third of the size 

 of the house-fly, but may be known by its shining black 

 body, scarlet head, and transparent wings, tipped with 

 black. This tiny little creature whether it trips over 

 a leaf, or remains stationary basking in the sunshine, is 

 continually vibrating its wings. < This motion,' says 

 Kirby, ' I have reason to think, assists its respiration;' 

 but as he has not stated his reason, we are led, from 

 an experiment which we tried, to doubt the conclusion. 

 Having always seen the fly vibrating its wings in the 

 sunshine only, as if it enjoyed the warmth and rejoiced 

 in the feeling of existence, we wished to see how it 

 would comport itself at night, and enclosed one under 

 an inverted wine-glass for observation. The conjec- 

 ture which we had formed appeared to be correct; for 

 though, when moving about the glass, it vibrated its 



* J, R. 



