STRENGTH OF WEBS AND POWER OF SPIDERS. 



239 



where it shows as a tissue of close texture. In the building of additions 

 to the web, however, the new part shows as a quite open plane of 

 mesh work. 1 



The webs of Medicinalis are often built in the angles of cellar 

 windows, along the sill, and in positions quite similar to that in which 

 the Batavia snake was caught. The strength of several snares, 



found in the cellars of the Academ y of Natural Sciences of 

 Philadelphia, was tested as follows : two webs bore up under 

 a pencil weighing sixty-eight grains ; several small webs bore a weight 

 of one-fourth and one-half ounce in corks spread over the surface, but 



FIG. 221. The pouch, web, tower, and cocoon of the Medicinal spider, Tegenaria medicinalis. 



broke down under an equal weight condensed into a small shell. One 

 web bore up easily, and apparently would have carried for an indefi- 

 nite period, the half ounce shell. It also sustained for a short period 

 a weight of one ounce, and then gradually gave way by the breaking 

 down of the thread attachments to the wall, without any yielding of 

 the sheet itself. 



The weight of a " striped snake," such as is alluded to, probably 

 our common garter snake, Eutaenia sirtalis, Linn., is accurately fifty-five 



1 The two webs (Fig. 221) measured: No. 1 (upper), 14 inches long across the hypothe- 

 nuse, by 10 inches deep; No. 2 (lower). 18 inches long across the sheeted part, 24 inches 

 across the meshed extension, depth 9 inches. 



