INTRODUCTION. 91 



and after it has been for a short time exposed to the 

 air, it is ready for flight. 



Other minute ichneumons deposit their offspring 

 in the eggs, or in the pupa of butterflies, and such 

 numbers are destroyed in this way, that it is evident- 

 ly one of the means employed by Providence to keep 

 within due limits a tribe of creatures which, if left 

 to propagate without restriction, would occasion in- 

 calculable mischief, by destroying almost every kind 

 of vegetable produce. 



Having thus attempted to sketch the general his- 

 tory of Butterflies, a subject of sufficient extent to 

 admit of much further detail, we now proceed to de- 

 scribe the species which have been ascertained to 

 inhabit Britain, reserving such additional historical 

 notices as may be necessary for the full elucidation 

 of the subject, till we come to treat of the genera 

 and species to which they respectively refer. 



