MOTIONS OF INSECTS. 329 



against gravity, both in a perpendicular and a prone 

 position. Dr. Hulse, in Ray's Letters, seems to have 

 furnished a clue that will very well explain this. I give 

 it you in his own homely phrase. " They," spiders, 

 " will often fasten their threads in several places to the 

 things they creep up ; the manner is by beating their 

 bums or tails against them as they creep along^" Fix- 

 ing their anus by means of a web, the anterior part of 

 their body, when they are resting, we can readily con- 

 ceive, would be supported by the claws and hairs of 

 their legs ; and their motion may be accomplished by 

 alternately fixing one and then 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 shep- 

 herd spiders [Phalajigium). The tarsi of these insects 

 are setaceous and nearly as fine as a hair, consist- 

 ing sometimes of more than forty joints, those toward 

 the extremity being very minute, and scarcely discerni- 

 ble, and terminating in a single claw. These tarsi, 

 which resemble antennae rather than feet, are capable of 

 every kind of inflexion, sometimes even 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 



• 65. 



