STRUCTURE OF WINGS. 343 



of a thick structure and easily expanded. They differ 

 in this from full-formed wings, which cannot be 

 stretched a hair's breadth without tearing them ; 

 whereas we have taken the wing of a butterfly on its 

 emerging from the chrysalis, and extended it to four 

 times its original expansion. That the fluids of the 

 body are at this period impelled into the wings, is 

 proved by an experiment tirst tried, we believe, by 

 Swammerdam, on the wings of bees. " The blood 

 in the bee," he says, " is a limpid fluid, as may be 

 observed, if a little part be at this time cut off" from 

 the wings ; for then the fluid exudes from the cut part, 

 appearing, by reason of the extreme smallness of the 

 blood-vessels, under the form of little pellucid globules, 

 which insensibly and by degrees increase into con- 

 siderable little drops." — " The wings of the bee have 

 likewise matiy pulmonary tubes, which, when the 

 nymph is casting its last skin, have also, together 

 with all the other parts, once more to throw oft' their 

 exuviae. After this, when these tubes are again dis- 

 tended by the freshly impelled air, and the air-vessels, 

 which have hitherto been contracted, are inflated and 

 distended with the same air, it follows that the whole 

 wing afterwards expands itself, and becomes thrice, 

 nay, four times larger than it was before. This 

 expansion of the wings depends, therefore, both upon 

 the impulsion of the air and of the blood; for at the 

 same time when the air is impelled into the wings, a 

 considerable quantity of blood is likewise driven into 

 the vessels of the wings." — " The female bees do not, 

 as the common bees and the male, come forth with 

 their wings folded up, but expanded and displayed, 

 and in a state ready for flight. On this account, the 

 all-wise Author of Nature has provided for them a 

 more spacious mansion, in which they may expand 

 their wings conveniently and ])roperly ; so that after 

 they have burst from their cells they may be pre- 



