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 a ." 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 (Phalangium). 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. 



