MOTIONS OF INSECTS. 333 
IOs 
eravity, 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?.” Fixing their anus 
by means of a web, the anterior part of their body, when 
they are resting, we can readily conceive, would be sup- 
ported 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, L.). 'The tarsi of these in- 
sects 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 antenne 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 in- 
equalities of the surface on which they repose, so that 
every joint may in some measure become a point of sup- 
port. Their eight legs also, which diverge from their 
body like the spokes from the nave of a wheel, give them 
ano. 
