504 MOTIONS OF INSECTS. 



I trust you will allow, from this mass of evidence, that the English 

 Arachnologists — may I coin this term ? — were cofrect in their account of 

 this singular phenomenon ; and think, with me, that Swammerdam (who, 

 however, admits that spiders sail on their webs), and after him De Geer, 

 were rather hasty when they stigmatized the discovery that these 

 animals shoot their webs into the air, and so take flight, as a strange and 

 unfounded opinion.^ The fact, though so well authenticated, is indeed 

 strange and wonderful, and affords another proof of the extraordinary 

 powers, unparalleled in the higher orders of animals, with which the Crea- 

 tor has gifted the insect world. Were, indeed, man and the larger 

 animals, with their present propensities, similarly endowed, the whole 

 creation would soon go to ruin. But these almost miraculous powers in 

 the hands of these little beings only tend to keep it in order and beauty. 

 Adorable is that Wisdom, Power, and Goodness, that has distinguished 

 these next to nothings by such peculiar endowments for our preservation 

 as if given to the strong and mighty would work our destruction. 



After the foregoing marvelous detail of the aerial excursions of our 

 insect air-balloonists, I fear you will think the motions of those which fly 

 by means of wings less interesting. You will find, however, that they 

 are not altogether barren of amusement. Though the wings are the prin- 

 cipal instruments of the flight of insects, yet there are others subsidiary to 

 them, which I shall here enumerate, considering them more at large under 

 the orders to which they severally belong. These are wing-cases {chjtra, 

 tegmina, and hcmehjtra) ; winglets (^aJuIce) : poisers (halteres) ; tailets 

 (caudulce) ; booklets (Jiamnli) ; base-covers (tegulfe), &lq. Besides, 

 their tails, legs, and even nntcnna, assist them in some instances in this 

 motion. 



As toings are common to almost the whole class, I shall consider their 

 structure here. Every wing consists of two membranes, more or less 

 transparent, applied to each other : the upper membrane being very strongly 

 attached to the nervures {iicurce), and the lower adhering more loosely, 

 so as to be separable from them. The nervures^ are a kind of hollow 

 tube, — above elastic, horny, and convex ; and flat and nearly membrana- 

 ceous below, — which take their origin in the trunk, and keep diminishing 

 gradually, the marginal ones excepted, to their termination. The vessels 

 contained in the nervures consist of a spiral thread, whence they appear 

 to be air-vessels communicating with the tracheae in the trunk. The 

 expansion of the wing at the will of the insect is a problem that can only 

 be solved by supposing that a subtile fluid is introduced into these ves- 

 sels"', which seem perfectly analogous to those in the w ings of birds, and 

 that thus an impulse is communicated to every part of the organ sufficient 

 to keep it in proper tension. We see by this, that a wing is supported 

 in its flight like a sail by its cordage.^ It is remarkable that those insects 

 which keep the longest on the wing, the dragon-flies {LibelluUna) for 



> Swamm. Bibl. Nat. ed. Hill, i. 24. De Geer, vii. 190. 



* French naluralists use this term (ncrvurc) for the veins of wings, leaves, ikc. restricting 

 nerve (uerf) to the ramifications from tiic brain and spinal marrow. We have adopted the 

 term, which we express in Latin by ticura, from the Greek vevpa. 



3 Recent observations by several distinguished microscopical naturalists fully confirm 

 this opinion. 



♦ Jurine, Hymenopt. 19. 



