338 INSECT TRANSFORMATIONS. 



body, by bending itself into the form of a crescent; 

 for if they were 'olistriicted, whilst wet, they could not 

 afterwards be set to rights. 



All these changes are perfected, according to Swam- 

 merdam, by the force of the circulating fluids and the 

 air, impelled by respiration, a fact of which, we think, 

 there cannot be any doubt. It is very seldom, how- 

 ever, that we can surprise insects at the precise mo- 

 ment of their transformation, as it is for the most part 

 very speedily accomplished, for the whole of the pre- 

 ceding evolutions are usually completed in ten or fif- 

 teen minutes. '• It happened by mere chance,' says 

 Swammerdam, '- that T observed them for the first time: 

 one of these vermicles adhered to a stone-wall in the 

 river Loire, and it was so softened by the water dash- 

 ing up against it, that it could only half perfect its 

 change, so that I took it partly free and partly yet 

 fixed in the skin. I once afterwards saw this change 

 in the large kind of dragon-fly (^M,shnal) which had 

 crept to land out of a small lake, and cast its skin sit- 

 ting in the grass.'* 



a, newly-hatched blow-fly magnified, showing the pulpy, 

 crumplej state of the wings, b, the wings dry and fully ex- 

 panded. 



* Bib]. Nat., vol. i, p. 98. 



