M. Virey's Observations on Aeronautic Spiders. 185 



" araneus subfuscus, minutissimis oculis e viola purpui-ascen- 

 tibus, tardipes, et gressu et figura cancro marino non adeo dis- 

 similis," observes, " Certe egregius funambulus est, et miri- 

 fice filorum ejaculatione delectatur : neque solum in aere, uti 

 superiores, vehitur ; sed ipse etiam ascensum velificationemque 

 molitiir, pedibus sc. arctiiis ad se invicem applicitis sese quo- 

 dammodo librat, cursum promovet regitque nihilo seciiis quam 

 si illi essent a natura concessae alae vel remorum ordines*." 

 The extreme liability of air to be put in motion, and the ex- 

 ceeding levity of the lines of very small spiders, are facts which 

 M. Virey, in the prosecution of his researches, has not at- 

 tended to with sufficient minuteness. This is evinced by his 

 supposing that in a close room the air could not be agitated 

 to such a degree as to affect the results of his experiments. 

 Have then, I would inquire, the temperature of the body, the 

 motion of the limbs, and the act of respiration been altogether 

 overlooked as causes of disturbance? It would appear that 

 they have ; no allusion whatever being made to them, in this 

 respect, by M. Virey, who even recommends that the hand be 

 passed before young spiders, when afloat, in order to deter- 

 mine whether they are supported by a line or not ; a proceed- 

 ing calculated to mislead the inquirer, if executed with haste, 

 as it generally must be, by disturbing the air and occasioning 

 a deflection of the line, which consequently might escape his 

 observation. 



These difficulties are entirely avoided by my mode of ex- 

 perimenting. The vessels containing the twigs on which the 

 spiders are placed being generally locked up in a book-case, 

 or put under bell-glasses, the tranquillity of the atmosphere 

 immediately surrounding the prisoners is ensured without de- 

 triment to their physical powers. If then they are endowed 

 with the capability of flying, what is to prevent them from ex- 

 ercising it when thus stimulated to exertion ? Every facility is 

 afforded them which they can enjoy when at liberty, except 

 that of air in motion ; yet they are never found to escape from 

 the twigs by flight, notwithstanding their best endeavours to 

 quit them are persisted in pertinaciously. I have tried this 

 experiment with several hundred spiders of nearly thirty dis- 

 tinct species, including the Epeira Diadema in various stages 

 of growth, and uniformly with the same success. In a calm 

 atmosphere they are quite incapable of regaining their liberty, 

 but it placed in a current of air, many species let out their 

 lines with the utmost facility, along which, when attached to 

 any object, they pass in security. 



* Dc Arancis, p, 85. 

 iV. .S. Vol. 1 0. No, 57. Sept. 1831. 2 B To 



