FLYING SPIDERS. 153 
upper end of the stalk and then descend one or two inches and 
return, allowing the air to carry upward the loose thread. At the 
same time it elevated its abdomen and the current, acting on the 
loop already formed, drew out the thread from the spinnerets until 
a sufficient quantity had passed, when it broke off the end attached 
to the stalk and floated away with the web. In this way he ob- 
served several individuals ascend. At the time there was no per- 
ceptible current in the atmosphere except the upward current 
caused by rarefaction. 
In the autumn of 1865, in Northwestern Iowa, passing along the 
smooth surface of the river in a boat, he observed something cross- 
ing the river with a skipping motion, striking the surface of the 
water at irregular intervals. Looking about he saw that the same 
thing was taking place at other points. Upon intercepting one, 
which he had watched almost from the opposite bank, he found it 
to be a small spider (Attus), from the abdomen of which threads 
of web extended several feet into the air, by which it was floated 
along. As it crossed the water, the air being cooler, it had de- 
scended, allowing the spider to touch the surface of the river. 
-~ To account for the ascent of threads and spiders various the- 
ories have been proposed. It was formerly supposed that the 
threads were thrown out from the spider as water is from a syr- 
inge, independently of any outside force, and that the threads 
were afterwards blown into the air carrying the spider with them. 
Some have thought that the spiders actually flew in the air with- 
out help from webs or from the wind, using their legs as wings. * 
Mr. Murray t believed that a spider could shoot its threads in 
any direction without reference to the wind. He says :— 
“ Contrary to the assertion that ‘spiders have no power of pro- 
lling their webs without assistance from the wind,’ I fearlessly 
assert that they can do so in an a mr, ee in which the oe leaf 
obe n 
in favor of the opinion of Mr. Blackwall. The aéronautic spider 
_ can propel its threads both horizontally and Aira and at all 
relative angles, in motionless air, and in an neste se agitated 
by winds ; nay, more, the aérial traveller can even dart its thread, 
to use a ‘nautical phrase, in the ‘wind’s eye.’ My opii and 
observations are based on many A of experiments. Q: 
- Virey, Ferussac’s Bulletin Sciences Naturelles. Tom 
t Memoirs Wiine erian Soc.,Vol. v, pt. 2,1826; and Loudon’s Mie a. Hist., Vol. i, 1829. 
