THE AERONAUTIC OR BALl.OOXIXCl IIAl'.IT. 



261 



cleared away, and during ascent ujton a droi)i)ed dragline after a s[)i(ler lias 

 thrown herself from her snare. But it hecame especially interesting at that 



moment, for at once it suggested an act of volition on the part 

 Control- ,,j.- (],|j Lycogij^ by which, in a measure at least, it might control 

 Descent. ^*® descent. Evidently the shortening of the overhanging thread 



operated like the furling of sails upon a vessel, and decreasing the 

 motion of the spider increased tlie influence of gravity upon the body, 

 which thus .sank toward the ground. At the same time, the diminution of 

 the surface of the thread above, and the increase of bulk at the mouth 

 (trifling as it might be), tended to increase the buoyancy of the whole, and 



allowed the creature to fall. The same effect was thus produced by the 

 spider aeronaut, and by a strikingly analogous mode, as that whirh tiie 

 human aeronaut accomplishes when he con- 

 tracts the surface of his balloon bv causiup- 

 the inflating gas to escape. 



The manner in which the lines of spi- 

 ders are carried out from the sjiinncrets by 

 a current of air a^ipears to be 

 Ho-wFila-|.]j^^g. ^g ^^ preparatory measure, 

 nients are ^, . . i ' i ^ • , 



p -ff J the spinnerets are brought into 



close contact, and the liquid silk 

 is emitted from the spinning tubes ; the 

 spinnerets are then separated by a lateral 

 motion, which breaks up the silk into fine 

 filaments; on these filaments the air current 

 impinges, drawing them out to a length 

 which is regulated by tlie will of the ani- 

 mal ; and, on the spinnerets being again 

 Ijrought together, the filaments coalesce and 

 form a compound line.' According to Mr. 

 Emerton,' the line seems to come from the middle pair of si>innerets 

 only, but the posterior pair Mere in constant motion, folding together 

 over the middle ones and then spreading ajjart as if to help throw out 

 the threads. 



Fio. 273. Fig. 274. 



Fni. 273. Floating with head depressed, 

 holding to a foot basket. Fifi. 274. Bal- 

 looning spider gathering in its threads 

 for descent. 



III. 



It will here be in place, and will add to the understanding of the 

 reader, to insert a few field notes giving in detail the above and some 

 further facts as to the posture and action of spiders before and during 

 flight. 



' ■' I'.lackwall on the Structure, Fnni'tions, and Kconomy of tlir .Vnineidea," .\nn. am 

 Mag. c.r Xat. Hist., Vol. XV., page 241, lS4o. 



-" Klying Spiders," Ameriatn Xatiiralist, I.S7L', i)age IG8. 



