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XX. Observations and Experiments, made with a view to ascertain 
the Means by which the Spiders that produce Gossamer effect 
their aérial Excursions. By John Blackwall, Esq., F.L.S. 
Read June 5, 1827. 
Arrnovucu 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 papillæ situated 
at the extremity of the abdomen, yet the manner in which these 
aérial 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 
the above conjectures, and for references to the sources from which they are derived, 
see the Introduction to Entomology by Kirby and Spence, Letter xxiii. 
3M 2 sition 
