62 AMERICAN SPIDERS 



The difficulties he enumerated are inherent in the spiders them- 

 selves and in their silk, and are still those that rule out the silk of 

 spiders as a potential material for commerce. In the first place, 

 spiders are solitary, predaceous animals that feed only on living 

 invertebrates. Each spider must be segregated and maintained apart 

 from its neighbor, for cannibalism is the rule when the larger 

 spiders come together, and the population is soon decimated. Space 

 requirements are considerable; the difficulties of providing suitable 

 food are almost insurmountable. Only the egg-sac silk was con- 

 sidered at that time to be usable, and, although many sacs are pro- 

 duced by the females, it would require, as de Reaumur estimated, 

 663,522 spiders to produce a pound of silk. On such terms, compe- 

 tition with the silkworm was impossible. 



The silk itself was considered inferior in strength to that of the 

 silkworm, owing to its far finer threads, which lacked the luster 

 of insect silk and were difficult to work satisfactorily. The silk- 

 worm produces a single line of silk, which is usually between four 

 and seven hundred yards long a production representing the total 

 output, the whole lifework, of the larval moth. Even with the 

 relatively thick lines of the silkworm, their joining together to form 

 commercially usable threads is an exacting process, which, because 

 no mechanical solutions have been successful, must be done by 

 hand. Strands of spider silk do vary in thickness, and the large silk 

 spiders of the genus Nephila, which abound in the East Indies and 

 in the Orient, produce a silk noted for its strength. However, state- 

 ments that the lines in the webs of Nephila sometimes attain the 

 thickness of darning wool are exaggerations. Their thickest line is 

 very much finer than that of the silkworm. 



In Madagascar an attempt was made to take silk from the local 

 spiders by drawing it directly from their bodies. The natives 

 brought the animals into cleared areas and established them in great 

 numbers near the site of the reeling apparatus. At intervals, the 

 mature spiders were removed from their webs and imprisoned in 

 a most curious device consisting of little stocks that held them 

 firmly between cephalothorax and abdomen. Then small revolving 

 mills were touched to each spinneret, and, as the filaments were 

 pulled out, they were rolled into a single thread by a hand-operated 

 mill. The silk so produced was of a beautiful golden color and quite 

 as good as that of the silkworm, but the project had to be aban- 

 doned because of the practical difficulties. 



In the United States, Dr. B. G. Wilder drew attention to the 



