362 INSECT TRANSFORMATIONS. 



Bechstein) furnishes a good example, putting itself 

 in a constant state of preparation, jerking its pie- 

 bald head up and down as it skips from stone to 

 stone of the brook, to pounce under water upon the 

 first grub it espies swimming. In the same way 

 the red-breast {Sylvia rubecula) pops jerking about 

 when on the look-out for caterpillars ; and so habitual 

 does this become, that he does not fail to go through 

 the manceuvre when he pecks up a crumb at the cot- 

 tage-door, as well as when he pounces upon a cater- 

 pillar in the woods, w^here 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 else- 

 where with the fanning butterflies {Vanessce) just 

 alluded to, we can scarcely (considering its size) ex- 

 pect to have attracted the notice of those who pay 

 little attention to insects. We allude to the vibrating 

 fly (Seioptera vibrans, 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 trans- 

 parent 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 conjecture which w'e had formed appeared to be 

 correct ; for though, when moving about the glass, 

 * J. R. 



