AND AMERICAN RURAL SPORTS. 



175 



force is unusually great, or the electricity of the atmos- 

 phere is remarkable for its intensity. 



But though each of the alleged causes just adverted to 

 appears incompetent to produce the required effect, yet one 

 abundantly adequate may perhaps be found in the phj'sical 

 endowments of the animals themselves, or in the extreme 

 lightness of their webs: these two last-named suppositions 

 therefore merit a careful examination. 



If the spiders do impel their lines upward by the volun- 

 tary exercise of some animal function which has hitherto 

 eluded the researches of physiologists, it follows, that when 

 the communication is interrupted, the lines, unless influ- 

 enced by some other force, must necessarily fall. Now the 

 reverse of this uniformly ensues: for if the insects, after 

 having commenced their ascent, are suddenly separated 

 from the lines to which they are attached, the latter still 

 continue to ascend, their motion being accelerated by their 

 diminished gravity, but the former are rapidly precipitated 

 to the ground. The conclusion is obvious. The buoyancy 

 of the lines cannot be occasioned by the beings which pro- 

 duce them; and the ascent of large flakes of web unoccupied 

 by spiders, before alluded to, confirms this opinion. 



Perhaps the buoyance of lines from which spiders have 

 been detached, and of webs although destitute of these in- 

 sects, may be regarded as facts powerfully contributing to 

 establish the idea that this animal secretion is specifically 

 lighter than the mixed gases which compose the atmos- 

 phere. The fallacy of this notion, however, is easily proved 

 by experiment. In the comparatively still air of a room 

 without fire, both the lines and webs descend slowly to the 

 floor, the latter falling with the greater degree of velocity. 



Were these productions lighter than atmospheric air, or 

 were the spiders capable of effecting an ascent without the 

 help of adventitious aid, a calm though cloudy daj'^ might 

 answer their purpose; but as considerable warmth is re- 

 quired to produce an ascending current of rarefied air 

 strong enough to bear them from the earth, a bright as well 

 as still day is indispensable. 



Founded on results obtained from an experiment which 

 has been frequently made, but never conducted with suffi- 

 cient care, is the belief entertained by many eminent en- 

 tomologists that spiders can forcibly propel or dart out 

 threads from their papillse. Now as this process would, 

 contrary to my own experience, imply the exercise of a 

 physical power peculiar to these creatures, and as attempts 

 have been made to explain on this principle the fabrication 

 of their webs in situations where their ordinary mode of 

 proceeding could not be employed, I determined to repeat 

 the experiment from which so strange a conclusion has been 

 deduced. With this view, having procured a small branch- 

 ed twig, I fixed it upright in an earthen vessel containing 



water, its base being immersed in the liquid, and upon it 

 I placed several of the spiders which produce gossamer. 

 Whenever the insects thus circumstanced were exposed to 

 a current of air, either naturally or artificially produced, 

 they directly turned the thorax towards the quarter whence 

 it came, even when it was so slight as scarcely to be per- 

 ceptible, and elevating the abdomen, they emitted from 

 their spinners a small portion of glutinous matter, which 

 was instantly carried out in a line, consisting of four finer 

 ones, with a velocity equal, or nearly so, to that with which 

 the air moved, as was apparent from observations made on 

 the motion of detached lines similarly exposed. The spi- 

 ders, in the next place, carefully ascertained whether their 

 lines had become firmly attached to any object or not, by 

 pulling at them with the first pair of legs; and if the result 

 was satisfactory, after tightening them sufficiently they 

 made them fast to the twigs; then discharging from their 

 spinners, which they applied to the spot where they stood, 

 a little more of their liquid gum, and committing them- 

 selves to these bridges of their own constructing, they pass- 

 ed over them in safety, drawing a second line after them as 

 a security in case the first gave way, and so effected their 

 escape. 



Such was invariably the result when the spiders were 

 placed where the air was liable to be sensibly agitated: I 

 resolved therefore to put a bell-glass over them; and in this 

 situation they remained seventeen days, evidently unable 

 to produce a single line by which they could quit the 

 branch they occupied without encountering the water at 

 its base ; though on the removal of the glass they re- 

 gained their liberty with as much celerity as in the instances 

 already recorded. 



This experiment, which from a want of due precaution 

 in its management has misled so many distinguished natu- 

 ralists, I have tried with several of the geometric spiders, 

 and always with the same success. Placed under the bell- 

 glass, or in any close vessel, they in vain endeavoured to 

 make their escape from the branch to which they were 

 confined, but in the disturbed air of an inhabited room 

 they readily accomplished their object. 



Instances of long-sustained abstinence from food by in- 

 sects of the genus Jiranea, unaccompanied b)' any mani- 

 fest diminution of vital energy, have been given by various 

 observers. In adding another case to the list it is proper to 

 remark, that it must be received solely on my own autho- 

 rity. 



Some of the spiders which produce gossamer were procur- 

 ed on the 2d of October, and inclosed in glass phials with 

 ground stoppers, where they were suffered to remain till the 

 16th of Deceniber, an interval of seventy-five days, without 

 either food or moisture; yet at the expiration of that period, 



