144 



AMERICAN SPIDERS AND THEIR SPINNINGWORK 



Zilla 

 atrica. 



stretched their characteristic webs diagonally across to tlie hand rail. It 

 thus happened that as many as a dozen or fifteen snares would be l)uilt 

 out from the same cornice or moulding, their upper foundations occupying 

 the same horizontal plane, but diminishing in length as they approached 

 the angle made by the post and the hand rail. The wedge shaped space 

 thus defined was almost completely filled with spinningwork, the orbs Viiry- 

 ing a good deal in size, but being alike in .structure. 



The position was a good one for trapping insects, whicli fly in vast 

 numbers over the surface of the streams, but I could not but wonder 

 whether some of the spiders occui)ying the interior snares were not sore 

 put to it to i)ick up an honest living, and might not have been constrained 

 to resort to cannibalism. However, I saw no raids " ower the border," 

 notwithstanding the traditions of the Scottish site, but all the aranead 

 clans seemed to be dwelling in peace. 



T had a .fine opportimity one summer of studying the si)imiing hal)it 



of Zilla atrica at Annisquam, Massachu- 

 setts. Many of tiiis species were colonizt'd 

 upon the sjtacious grounds and 

 surroundings of the j)lace where 

 I was lodged. They were domi- 

 ciled upon the chicken coops and outbuild- 

 ings, upon the shrubbery, and in consiilcr- 

 able numbers upon the boat house on the 

 very verge of the inlet. In the latter po- 

 sition their snares were swung just above 

 the point of high tide, and they were very 

 busy capturing the insects that flew around 

 and above the water, and defending them- 

 selves from vigorous colonies of Epeira patagiata domiciled in the .sauie site. 

 I noticed an occasional tendency among these Zillas to spin a full 

 round orb. For example, in one colony of fourteen, all the nests were 

 sectoral except one. In another of fifteen, fourteen were sectoral, and one 

 had a complete orb. I could observe no obvious reason from 

 the nature of the location why this difference .should apj)ear. It 

 evidently is characteristic of the genus. Zilla calloi)h3'la, a 

 European species, can usually be recognized among the British 

 Orbweavers by the open sector, which characterizes its web. 

 This peculiarity, however, does not always exist, as webs formed by young 

 individuals, probably of the same brood, are occasionally found within a 

 short distance of each other, some with the characteristic free radii, others 

 Cdustrueted after the usual Epeira type.i There appears, thus, in ]>oth 

 bcmisiihcres to be a tendency in this genus to revert to the typical round 



Fig. 134. 



Fig. 135. 



l-'iGS. 134, 135. Complex or branched traplines 

 of Zilla. S, the spider ; S.R., sectoral radius. 



Excep- 

 tional 

 Round 

 Webs. 



' Stiiveley, "Britis^h fiiidorn," pajie 247. 



