BRITISH BUTTERFLIES. 



THE BUTTERFLY. 



When the time for the final change has ar- 

 rived, the colours and markings of the perfect 

 insect begin to make their appearance through 

 the horny shell which envelopes the chrysalis, 

 and in a short time this horny shell splits in 

 various places, cracks open between pieces of 

 the shell, and the perfect insect emerges. I 

 say perfect, but, alas, how apparently imper- 

 fect 1 The wings, instead of being those rigid 

 and powerful organs which are soon to become 

 so characteristic of a butterfly, and are so well 

 adapted to bear him on the most distant aerial 

 excursions, are diminutive, shapeless abor- 

 tions, folded over his chest, limp, pliable bags, 

 filled with colourless blood which has hereafter 

 to be diffused throughout the body. " To ob- 

 serve how gradual and yet how rapid was the 

 development of the joints and organs, and 

 particularly of the wings, and the perfect 

 coming forth of the colours and spots as the 

 sun gave vigour to it, was a more interesting 

 spectacle." I will continue to quote Kirby and 

 Spence, for, although I can readily imagine no 

 one has so long or so intently studied these 

 proceedings of Nature as I have done, yet I 

 feel painfully conscious of my inability to 

 describe them with the force and truthfulness 

 that so distinguish the writings of those 

 illustrious entomologists. They are describing 

 the emergence of the Swallow-tail : " At 

 first it was unable to elevate or even move its 

 wings, but in proportion as the aerial or other 

 fluid was forced by the motion of its trunk 

 into the nervures, their numerous corrugations 

 and folds gradually yielded to the action, till 

 they had gained their greatest extent, and the 

 film between all the nervures became tense. 

 The ocelli and spots and bars, which appeared 

 at first as but germs or rudiments of what 

 they were to be, grew with the growing wing, 

 and shone forth upon its complete expansion 

 in full magnitude and beauty. To understand 

 more clearly the cause of this rapid expansion 

 and development of the wings, I have before 

 explained that these organs, though often ex- 

 ceedingly thin, are always composed of two 



membranes, having most commonly a number 



of hollow vessels, miscalled nerves, running 

 between them. These tubes which, after the 

 French entomologists, I would name nervures 

 contribute as well to the development of the 

 wings as to their subsequent tension. In the 

 chrysalis, and commonly after wai'ds, the two 

 membranes composing the organs in question 

 do not touch each other's inner surface as they 

 afterwards do : there is consequently a space 

 between them j andbeingmoist and corrugated 

 into a vast number of folds, like those of a fan, 

 but transverse as well as longitudinal, and so 

 minute as to be imperceptible to the naked 

 eye, the wing appears much thicker than 

 in the end. Now, as soon as the insect is 

 disclosed a fluid enters the tubes, and being 

 impelled into their minutest ramifications, ne- 

 cessarily expands their folds ; for the nervures 

 themselves are folded, and as they gradually 

 extend in length with them, the moist mem- 

 branes attached to them are also unfolded and 

 extended. In proportion as this takes place 

 the expanding membranes approach each 

 other, and at last, being dried by the action 

 of the atmosphere, become one. To promote 

 this motion of the fluid seems tho object ot 

 the agitations which the animal gives from 

 time to time to its unexpanded wings." 



That a fluid precisely analogous to our 

 blood, but having no red colour, circulates in 

 every part of an insect's body, has been proved 

 beyond question. Dr. Bowerbank was the 

 first entomologist in this country who by 

 means of a powerful microscope established 

 the fact; and although prior to this important 

 discovery there was a disposition to doubt the 

 existence of circulation in the insect world, 

 every man of science at once accepted Dr. 

 Bowerbank's views as conclusive ; and no 

 hesitation is now expressed on a subject where 

 an exception to the ordinary law of Nature 

 had been for a series of years supposed not 

 only possible but unquestionable so ready 

 are we to accept any conclusions that super- 

 sede the trouble of investigation. 



We have seen that the membranous portior. 

 of the wing is spread between certain supports, 

 which Messrs. Kirby and Spence, adopting the 

 nomenclature of French ent. .moiogists, have 



