CONSTRUCTION OF AN ORBWEB. 63 
the wind directly from spiders’ spinnerets, have observed the entanglement, 
have seen the animal draw the threads taut and then cross upon them. 
That all the lines are similarly formed and used I have no doubt. 
Mr. Terby, in a paper contributed in 1867 to the Royal Academy of 
Belgium, makes a number of intelligent and accurate observations upon the 
habit of spiders to throw out their floating threads in order to 
‘secure passage from point to point. He demonstrated by numer- 
ous experiments that these threads could not be projected by the power of 
the spider without the aid 
of the wind. I regret that 
I only happened to fall 
upon this paper after the 
completion of my manu- 
script, so that I can insert 
here but a brief allusion to 
it.1 Blackwall also had ob- 
served as much 
cre and gives a brief 
and accurate de- 
scription. The manner, he 
says, in which the lines of 
spiders are carried out from Wi \ IN 
the spinners by a current of SY 
air appears to be this: as 
a preparatory measure, the 
spinnerets are brought into 
close contact and _ viscid 
matter is emitted from the 
spinning spools. They are 
then separated by a lateral 
motion, which extends the = < 
? - - 
viscid matter into fine fil- Corde, ere s 
aments, connecting the = 
spools. On these filaments 
the current of air impinges, 
drawing them out from the spinnerets to a length which is regulated 
by the will of the animal, and on the spinnerets being again brought to- 
gether the filaments coalesce and form one compound line.? 
It is a more difficult matter to determine whether the lines used for the 
foundations of orbwebs are formed in the same way. I have seen an orb- 
weaver, after traversing a considerable space by a series of successive bridge 
M. Terby 
1 
oy Gq He taemasg 
(Aine 
oa 
Fic. 61. A colony of spiders domiciled over water. 
* M. F. Terby, sur les procédés qu’emploient les araignées pour relier des points eloignés par 
un fil. Bull. l’Académie Royale de Belgique, 1867, page 274, sq. 
* Researches in Zoology, page 269. 
