502 MOTIONS OF INSECTS. 



diurnal flights. But Dr. Strack's observations render this very doubtful ; 

 for he kept many of the spiders that produce these webs in a large glass 

 upon turf, where they spun as when at liberty, and he could never observe 

 them attempt to catch or eat — even when entangled in their webs — the flies 

 and gnats with which he supplied them ; though they greedily sucked water 

 when sprinkled upon the turf, and remained lively for two months without 

 other food.^ As the single threads shot by other spiders are usually their 

 bridges, this perhaps may be the object of the webs in question ; and thus 

 the animals may be conveyed from furrow to furrow or straw to straw less 

 circuitously, and with less labor, than if they had traveled over the ground. 

 As these creatures seem so thirsty, may we not conjecture that the drops 

 of dew, with which they are always as it were strung, are a secondary 

 object with them ? So prodigious are their numbers, that sometimes every 

 stalk of straw in the stubbles, and every clod and stone in the fallows, 

 swarms with them. Dr. Strack assures us that twenty or thirty often sit 

 upon a single straw, and that he collected about 2000 in half an hour, 

 and could have easily doubled the number had he wished it : he remarks, 

 that the cause of their escaping the notice of other observers is their fall- 

 ing to the ground upon the least alarm. 



As to what becomes of this immense carpeting of web there are diffe- 

 rent opinions. Mr. White conjectures that these threads, when first shot, 

 might be entangled in the rising dew, and so drawn up, spiders and all, 

 by a brisk evaporation, into the region where the clouds are formed.^ 

 But this seems almost as inadmissible as that of Hooke, before related. 

 An ingenious and observant friend, thinking the numbers of the flying 

 spiders not sufficient to produce the whole of the phenomenon in question. 

 is of opinion that an equinoctial gale, sweeping along the fallows and 

 stubbles coated with the gossamer, must bring many single threads into 

 contact, which, adhering together, may gradually collect into flakes ; and 

 that being at length detached by the violence of the wind, they are carried 

 along with it: and as it is known that such winds often convey even sand 

 and earth to great heights, he deems it highly probable that so light a sub- 

 stance may be transported to so great an elevation as not to fall to the 

 earth for some days after, when the weather has become serene, or to 

 descend upon ships at sea, as has sometimes happened. This, which is 

 in part adopted from the German authors, is certainly a much more reason- 

 able supposition than the other; but some facts seem to militate against 

 it: for, in the first place, though gossamer often occurs upon the ground 

 when there is none in the air, yet the reverse of this has never been 

 observed ; for gossamer in the air, as in the instance recorded by Mr. 

 White, is always preceded by gossamer on the ground. Now, since the 

 weather is constantly calm and serene when these showers appear, it can- 

 not be the wind that carries the web from the ground into the air. Again, 

 it is stated that these showers take place after several calm days^; but, if 

 the web was raised by the wind into the air, it would begin to fall as soon 

 as the wind ceased. Whence 1 am inclined to think that the cause 

 assigned by Dr. Lister is the real source of the whole phenomenon. 

 Though ordinary observers have overlooked them, he noticed these spiders 



> Neue Schriften der Naturforschenden GesseUschaft zii ITalle, IS 10, v. Ihft. 

 * Nat. Hist. i. 326. s Ray's Lelteis, 36. 



