28 NATURAL HISTORY. [CH. I. 



brane between the tubes or nervures becomes at the 

 same time extended to its proper size, when it very 

 quickly dries by the action of the atmosphere. The 

 experiments of Swammerdam and Reaumur suffi- 

 ciently elucidate these facts, from which it would 

 appear that an aeriform as well as an aqueous fluid is 

 injected into the tubes, and hence it is that the in- 

 sect, when newly disclosed, agitates its unfolded 

 wings for the purpose of putting these fluids in mo- 

 tion. Indeed, according to Swammerdam, a violent 

 agitation is produced in the fluids of the butterfly, 

 so that they are driven from the internal vessels 

 into the tubes of the wings, which are likewise 

 supplied with air from the tracheae. The manner 

 in which the wings are wrinkled when closed is 

 admirably adapted for the easy extension of the 

 connecting membrane ; for although the wing ap- 

 pears at first to be much thicker than it subsequently 

 is, yet the appearance is not real, being only pro- 

 duced by the two layers of membranes not being 

 applied to each other, so that there is a space be- 

 tween them, and also by the surface of each mem- 

 brane being entirely covered with wrinkles, so very 

 minute as to be almost invisible to the naked eye. 

 Consequently it is to be observed, that these wings 

 are not, as might be imagined, folded up like the 

 wings of a beetle or an earwig, and hence it is that 

 on the first extrication of the butterfly all the future 

 markings of the wing are visible, but of a very di- 

 minished size. 



It is a curious question, and one which we believe 

 has not hitherto been noticed, in what manner the 

 downy scales of the wings are at this time disposed, 

 and whether they increase in size, since it is to be 

 observed, that it is to these scales, which are so 

 densely planted both upon the upper and the under 

 surface of the wings, and not to the substance of 

 the wing itself, that the butterfly owes all its gor- 

 geous colours. According to De Geer these should 



