207 [Wilder. 



a spider at one time; but this evidently does not exhaust the supply, 

 for on opening the abdomen the glands are still partially filled and the 

 following day a quantity equal to the fii-st may be obtained ; this I did 

 upon three successive days, so that, if, as now seems probable, the 

 emission of the silk is mainly mechanical, then a certain degree of 

 preparation is necessary after it is secreted before it is ready for use. 



The diameter of the silk as spun by the insect or as reeled from it, 

 varies from -^^^ to j-^^q of an inch ; * it is exceedingly strong, but I 

 have not yet been able to accurately determine its strength as com- 

 pared with fine ordinary silk. The largest threads are those compos- 

 ing the outer layer of the cocoons, but these are evidently compound, 

 and the two, three or four strands are apparently such as proceed from 

 the single spinners, the minute fibrils of which have united at once on 

 leaving the spinnerules so as to form the ordinary silken fibre which 

 generally appears simple under the microscope. 



Having completed her web, the female stations herself at its centre 

 head downward, waiting for prey ; the diminutive male (they are not con- 

 stantly present) preserves a respectful distance fix)m her, and, as far 

 as I have seen, never attempts to do anything for himself, except of 

 course the impregnation of the eggs ; he builds no web and catches no 

 prey ; and while she is moving from place to place, or even while mak- 

 ing her web, he gets upon the upper or lower side of her abdomen 

 holding on with his legs and darting about to keep out of the way of 

 hers ; for she seems to pay no attention to him and might easily do 

 him an injury even by accident. 



On one occasion I saw a male stray away from his proper home to 

 an adjoining web, from which, however, he was speedily driven by the 

 indignant female possessor, with the loss of two of his legs ; of which 

 injury he shortly afterwards died. 



Li the webs of these spiders are found insects of all kinds, even the 

 largest and most vigorous, such as the great cicada of the South. 

 When anything strikes the web, the spider instantly starts, and, if the 

 vibrations indicate that it is suitable for food she rushes to it and seiz- 

 ing it in her powerful jaws holds on till it is dead ; after which she 

 throws a net around it and carries it to a place where she can devour 

 it at her leisure ; in this respect unlike some other geometrical spiders, 

 of which one species, common on James Island, S. C, never attempts 

 to seize the prey with the jaws till it has first dexterously spread a net 

 over it by turning it over and over with the first and third pairs of 

 legs and, with the fourth pair, used alternately, drawing out the silk 

 as a broad white band. 



But if the violent struggles of the prey show it to be of large size, 

 then our spider advances with caution, feeling with her anterior legs, 



♦The micrometer measurements were made by Mr. K. C. Greenleaf. 



