RESEARCHES UPON SPIDERS. 61 



IV. 



QUANTITY OF SILK PRODUCED FROM SPIDERS. 



Reaumur, intent on showing that no commercial advan- 

 tage can be drawn from the silk of the spiders, endeavors 

 to prove that but a very small quantity can be collected ; 

 and, in the first place, he makes a comparison between the 

 cocoons of the common silk- worm, and those of spiders ; 

 and finds, that one of the first weighs about four grains, 

 whereas the cocoon of even a large spider weighs hardly 

 one grain ; and this being also, for the most part, mixed with 

 dust and with the shells of the eggs, it follows that the silk 

 of a spider's cocoon, will be hardly one twelfth of the cocoon 

 of the silk-worm. It may be added, he says, that all the 

 silk-worms produce cocoons, while among spiders it is 

 only the females that make them. He concludes, therefore, 

 that 55296 of the largest spiders are necessary to produce 

 a pound (16 oz.) of silk; while .2304 cocoons of the silk- 

 worm are sufficient for the same result, and thence he argued 

 that rearing them is not promising and can not be made 

 profitable. 



But in this calculation of Reaumur's there are many 

 data to rectify. 1st. There are very few cocoons of the 

 silk-worm which weigh four grains ; generally, unless they 

 are made to work inclosed in paper boxes, they do not weigh 

 more than three grains, and De Pluche found that they did 

 not exceed two and a half grains. 2nd. He attributes to 

 the spiders, as to the silk-worms, only one cocoon a year, 

 and we have observed and shall see in what follows, that 

 sometimes they produce even six. 3rd. He says that the 

 cocoon of a spider, even of the largest kind, hardly weighs 

 a grain, whereas I have found a much greater weight, I am 

 certain that two cocoons of an A merican spider, the species 

 of which I have not yet determined, weighed as much as one 

 of the silk-worm's before being cleansed ; and after being 

 cleansed, they had lost less than half their weight. In 

 America, moreover, I found some cocoons of those very large 

 spiders, called by Linnaeus Aranea avicularis because they 

 carry away even humming birds from their nests, which 

 weighed as much as six cocoons of the silk- worm when they 



