306 INSECT ARCHITECTURE. 



for her previously attaching and drawing oat a thread from 

 the glass, the wish to give the wind a point d'appui — some- 

 thing upon which it might have a purchase, as a mechanic 

 would say of a lever. The bend of the thread, then, on this 

 view of the matter, would be carried out by the wind, — 

 would form the point of impulsion, — and, of course, the 

 escape bridge would be an ordinary line doubled. 



Such was our conclusion, which was strongly corro- 

 borated by what we subsequently found said by M. Latreille 

 — than whom no higher authority could be given. " When 

 the animal," says he, " desires to cross a book, she fixes to 

 a tree or some other object one of the ends of her first 

 threads, in order that the wind or a current of air may carry 

 the other end beyond the obstacle ;"* and as one end is 

 always attached to the spinnerets, he must mean that the 

 double of the thread flies off. In his previous publications, 

 however, Latreille had contented himself with copying the 

 statement of Dr. Lister. 



In order to ascertain the fact, and put an end to all 

 doubts, we watched, with great care and minuteness, the 

 proceedings of the long-bodied spider above mentioned, by 

 producing a stream of air in the same manner, as it peram- 

 bulated the brim of the glass. It immediately, as the 

 other had done, attached a thread and raised its body per- 

 pendicularly, like a tumbler standing on his hands with his 

 head downwards ; but we looked in vain for this thread 

 bending, as we had at first supposed, and going off double. 

 Instead of this it remained tight, while another thread, or 

 what appeared to be so, streamed off from the spinners, 

 similar to smoke issuing though a pin-hole, sometimes in a 

 line, and sometimes at a considerable angle, with the first, 

 according to the current of the air, — the first thread, ex- 

 tended from the glass to the spinnerets, remaining all the 

 while tight drawn in a right line. It further appeared to 

 us, that the first thread proceeded from the pair of spin- 

 nerets nearest the head, while the floating thread came 



* " L'un des bouts de ces premiers fils, afin que le vent ou un 



courant d'air pousso I'autre estre'mite de l'un d'eux au de la de 

 robstacle,"— Diet. Classique d'Hist. Nat,, vol. i. p. 510. 



