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XX. Observations and Experiments, made rvith a view to ascertain 

 the Means by which the Spiders that produce Gossamer effect 

 their aerial Excursions. Bi/ John Blackwall, Esq., F.L.S. 



Read June 5, 1827. 



Although it is well known that spiders sometimes ascend into 

 the atmosphere through the instrumentality of fine lines of a 

 viscous gummy matter, which proceed from the papillœ situated 

 at the extremity of the abdomen, yet the manner in which these 

 aerial journeys are effected still remains involved in obscurity, 

 and considerable diversity of opinion exists as to the particular 

 species of spider by which they are undertaken. This deficiency 

 leaves open a wide field for speculation ; and accordingly we 

 find, that natural historians have ascribed this interesting occur- 

 rence to several distinct causes, — such as the agency of winds, 

 evaporation, and electricity ; the exercise of peculiar physical 

 powers, with which the spiders that produce gossamer have been 

 supposed to be endowed ; and the extreme levity of the webs of 

 these insects, which are represented by some writers on the sub- 

 ject to be of less specific gravity than atmospheric air*: but 

 that each of these hypotheses is unfounded, and in direct oppo- 



* For a concise statement of the principal circumstances which have given rise to 

 tlie above conjectures, and for references to the sources from which they are derived, 

 see the Introduction to Entomology by Kirby and Spence, Letter xxiii. 



3 M 2 sition 



