POPULAR SCIENCE 



SOME RESULTS OF OBSERVATIONS ON THE ECONOMY 

 OP THE HOUSE SPIDER, TEG EN ARIA ATRICA. By 



Theodore Savory, Exhibitioner of St. John's College, Cambridge. 



The ease with which house spiders, or in fact any sedentary- 

 spider, may be kept alive in captivity is partly responsible for 

 many observations which, while they are of the greatest interest 

 to the specialist in arachnology, may be of some value to the 

 general zoologist. A brief note of a few of these appeared in 

 the Field of January 9, 191 5, and it is here proposed to con- 

 tinue and elaborate them. 



We have all watched the garden spider, when uncertain of 

 its prey's presence on the outskirts of its web, give one of the 

 threads a tug which decides the question. The house spider's 

 modification of this is of peculiar interest. Its tarsi fixed in 

 the silken sheet, it draws in each leg a distance of a millimetre 

 or two, thus decreasing the perimeter of the figure surrounding 

 it, and giving just that twitch to the web that is required to 

 make a fly or other insect move on. As the garden spider 

 wraps up its captive, so does the house spider, lest its struggles 

 irrevocably destroy the web. For this purpose it holds the fly 

 down on to the sheet of the web, and, itself walking around 

 it, twists it up in sufficient silk to suppress it. 



There is, I believe, a little rhyme about a centipede, which 

 runs — 



A centipede was happy quite 



Until a toad in fun, 

 Cried "Pray, which leg moves after which?" 

 This roused her doubts to such a pitch, 

 She fell exhausted in a ditch, 



Not knowing how to run. 



Wondering myself how a spider ordered the movements of its 

 eight legs, I allowed several to tire themselves by struggling 

 on the surface of water and then set them to run slowly over a 



246 



