498 



HISTORY OF INSECTS. 



inclosed within the covering of the aurelia, 

 continues to keep its body in the most tender 

 state, so it is requisite that this humidity 

 should be dried away, before the little butter- 

 fly can burst its prison. Many have been the 

 experiments to prove that nature may in this 

 respect be assisted by art ; and that the life of 

 the insect may be retarded or quickened, with- 

 out doing it the smallest injury. For this 

 purpose, it is only requisite to continue the 

 insect in its aurelia state, by preventing the 

 evaporation of its humidity ; which will conse- 

 quently add some days, nay weeks, to its life : 

 on the other hand, by evaporating its moisture 

 in a warm situation, the animal assumes its 

 winged state before its usual time, and goes 

 through the offices assigned its existence. To 

 prove, this, Mr Reaumur enclosed the aurelia 

 in a glass tube ; and found the evaporated 

 water, which exhaled from the body of the 

 insect, collected in drops at the bottom of the 

 tube : he covered the aurelia with varnish ; 

 and this making the evaporation more difficult 

 and slow, the butterfly was two months longer 

 than its natural term in coming out of its 

 case: he found, on the other hand, that by 

 laying the animal in a warm room, he hasten- 

 ed the disclosure of the butterfly ; and by 

 keeping it in an ice-house, in the same manner 

 he delayed it. Warmth acted, in this case, 

 in a double capacity: invigorating the animal, 

 and evaporating the moisture. 



The aurelia, though it bears a different ex- 

 ternal appearance, nevertheless contains with- 

 in it all the parts of the butterfly in perfect 

 formation ; and lying each in a very orderly 

 manner, though in the smallest compass. 

 These, however, are so fast and tender, that 

 it is impossible to visit without discomposing 

 them. When either by warmth, or increas- 

 ing vigour, the parts have acquired the neces- 

 sary force and solidity, the butterfly then seeks 

 to disembarrass itself of those bands which 

 kept it so long in confinement. Some insects 

 continue under the form of an aurelia not 

 above ten days ; some twenty ; some several 

 months ; and even for a year together. 



The butterfly, however, does not continue 

 so long under the form of an aurelia, as one 

 would be apt to imagine. In general those 

 caterpillars that provide themselves with cones, 

 continue within them but a few days after the 

 cone is completely finished. Some, however, 

 remain buried in this artificial covering for 

 eight or nine months, without taking the 

 smallest sustenance during the whole time : 

 and though in the caterpillar state no animals 

 were so voracious, when thus transformed they 

 appear a miracle of abstinence. In all, sooner 

 or later, the butterfly bursts from its prison ; 

 not only that natural prison which is formed 

 by the skin of the aurelia, but also from that 



artificial one of silk, or any other substance in 

 which it has enclosed itself. 



The efforts which the butterfly makes to 

 get free from its aurelia state, are by no means 

 so violent as those which the insect had in 

 changing from the caterpillar into the aurelia. 

 The quantity of moisture surrounding the but- 

 terfly is by no means so great as that attending 

 its former change ; and the shell of the aurelia 

 is so dry, that it may be cracked between the 

 fingers. 



If the animal be shut up within a cone, the 

 butterfly always gets rid of the natural inter- 

 nal skin of the aurelia, before it eats its way 

 through the external covering which its own 

 industry has formed round it. In order to 

 observe the manner in which it thus gets rid 

 of the aurelia covering, we must cut open the 

 cone, and then we shall have an opportunity 

 of discovering the insect's efforts to emancipate 

 itself from its natural shell. When this oper- 

 ation begins, there seems to be a violent agi- 

 tation in the humours contained within the 

 little animal's body. Its fluids seem driven 

 by a hasty fermentation, through all the ves- 

 sels ; while it labours violently with its legs, 

 and makes several other violent struggles to 

 get free. As all these motions concur with 

 the growth of the insect's wings and body, it 

 is impossible that the brittle skin which co- 

 vers it should longer resist : it at length gives 

 way by bursting into four distinct and regular 

 pieces. The skin of the head and legs first 

 separates ; then the skin at the back flies open, 

 and dividing into two regular portions, disen 

 gages the back and wings : then there like- 

 wise happens another rupture, in that portion 

 which covered the rings of the back of the 

 aurelia. After this, the butterfly, as if fa- 

 tigued with its struggles, remains very quiet 

 for some time, with its wings pointed down- 

 wards, and its legs fixed in the skin which it 

 had just thrown off. At first sight the animal, 

 just set free, and permitted the future use of 

 its wings, seems to want them entirely ; they 

 take up such little room, that one would won- 

 der where they were hidden. But soon after 

 they expand so rapidly, that the eye can scarce 

 attend their unfolding. From reaching scarce 

 half the length of the body, they acquire, in 

 a most wonderful manner, their full extent 

 and bigness, so as to be each five times larger 

 than they were before. Nor is it the wings 

 alone that are thus increased ; all their spots 

 and paintings before so minute as to be scarce 

 discernible, are proportionably extended; so 

 that what a few minutes before seemed only 

 a number of confused unmeaning points, now 

 become distinct and most beautiful ornaments. 

 Nor are the wings, when they are thus expanded, 

 unfolded in the manner in which earwigs and 

 grasshoppers display theirs, who unfurl them 



