498 MOTIONS OF INSECTS. 



the Other. But you will remember I give you this merely as conjecture, 

 having never verified it by observation.^ 



It may not be amiss to mention here another apterous insect that reposes 

 on perpendicular or prone surfaces, without either suckers or any viscous 

 secretion by which it can adhere to them. I mean the long-legged or 

 shepherd spiders (Phcdangiuni). The tarsi of these insects are setaceous, 

 and nearly as fine as a hair, consisting sometimes of more than forty joints, 

 those toward the extremity being very minute, and scarcely discernible, 

 and terminating in a single claw. These tarsi, which resemble antennae 

 rather than feet, are capable of every kind of inflexion, sometimes oven 

 of a spiral one. These circumstances enable them to apply their feet to 

 the inequalities of the surface on which they repose, so that every joint 

 may in some measure become a point of support. Their eight legs also, 

 which diverge from their body like the spokes from the nave of a wheel, 

 give them equal hold of eight almost equidistant spaces, which, doubtless, 

 is a great stay to them. 



The next species of locomotion exhibited by perfect insects \s Jiying. 

 I am not certain whether under this head I ought to introduce the sailing 

 of spiders in the air ; but as there is no other under which it can he more 

 properly arranged, I shall treat of it here. I shall therefore divide flying 

 insects into those that fly without v/ings, and those that fly with them. 



I dare say you are anxious to be told how any animals can fly without 



wings, and wish me to begin with them. As an observer of nature, you 



have often, without doubt, been astonished by that sight occasionally 



noticed in fine days in the autumn, of webs — commonly called gossamer 



webs — covering the earth and floating in the air ; and have frequently 



asked yourself — What are these gossamer webs ? Your question has from 



old times much excited the attention of learned naturalist. It was an old 



and strange notion that these webs were composed of dew burned by 



the sun. 



" The fine nets which oft we woven see 



Of scorched dew," 



says Spenser. Another, fellow to it, and equally absurd, was that adopt- 

 ed by a learned man and good natural philosopher, and one of the first 

 fellows of the Royal Society, Robert Ilooke, the author of Microgrophia, 

 " Much resembling a cobweb," says he, " or a confused lock of these 

 cylinders, is a certain white substance which, after a fog, may be observed 

 to fly up and down the air: catching several of these, and examining 

 them with my microscope, I found them to be much of the same form, 

 looking most like to a flake of worsted prepared to be spun ; though by 

 what means they should be generated or produced is not easily imagined : 

 they were of the same weight, or very little heavier than the air ; and 'tis 

 not unlikely but that those, great ivhite clouds, that a])pear all the summer 

 time, may be of the same substance.''^ So liable are even the wisest men 



> Mr. l^lackwall, as before stated, conceives that the power possessed by spiders which 

 use no threads, such as Drassns melatw^nsler, Salticus srenicus, tec, of walking up polished 

 surfaces, is derived from an adhesive fluid emitted from the tubular hair-like appendages of 

 their tarsi. (Linn. Trans, xvi. 480. IW.) 



* Microgr 202. It has been objected lo an excellent primitive writer (Clemens Bomanus), 

 that he believed the absurd fable of the phcrnix. But surely this may be allowed for Id 

 him, who was no naturalist, when a scientific natural philosopher could believe that the 

 clouds are made of spiders' web! 



