xiv SHEET-WEBS 353 



The snares of these spiders are exceedingly closely woven of 

 very fine silk, and take a long time to complete. The process of 

 their construction may be watched by keeping an Agelena 

 Idbyrinthica confined in a box with a glass front, and the web, 

 kept free from dust, is a beautiful object, as its fine texture 

 gradually becomes visible as a delicate transparent film which 

 develops by imperceptible stages into an opaque white sheet. 

 The excessive fineness of the silk makes it difficult at first to see 

 what is taking place. The animal is seen to be busily moving 

 about, but the result of its labours only gradually becomes visible. 

 A few delicate foundation -lines are first stretched across the 

 compartment in which it is confined, and upon these the spider 

 walks to and fro incessantly with a serpentine motion, and by 

 and by a muslin-like floor of silk comes into view. 



An examination of the spinnerets throws some light upon 

 the operation. The posterior pair are very long and mobile, and 

 the hair -like spinning-tubes are distributed on their under 

 surface. The cephalo thorax and abdomen are far more rigidly 

 connected in Agelena than in the Orb-weavers, but its length of 

 leg and the length and mobility of its posterior spinnerets 

 enable it to give a wide lateral sweep as it walks along, strewing 

 fine silken threads upon the foundation-lines already laid down. 

 Some hours elapse before even a moderately stout web is con- 

 structed, and for long afterwards the spider devotes odd 

 moments of leisure in going over the ground again and strewing 

 new silk upon the gradually thickening web. At one corner a 

 silken tube of similar structure is formed, and in Ibis the spider 

 awaits the .advent of any insect which may alight upon the sheet, 

 when it immediately rushes forth and seizes it. 



The webs of the Dictynidae are very similar in general 

 appearance to those of the Agelenidae, consisting of a closely- 

 woven sheet with a tubular nest. They are to be found, more- 

 over, in similar situations, stretching across the angles of walls 

 in cellars or outhouses, though some species prefer an outdoor 

 existence. Crannies in rock form convenient sites for such 

 snares, but the family is not without its representatives in si ill 

 more open situations. The web, 1 hough so similar to that of 

 Agelena, is, however, constructed in a different mannrr. In the 

 Dictynidae neither the Ic^s nor the spinnerets are unusually Ion-. 

 and thev do not strew the foundation-lines hv a s\\ iii'dii"- mot ion 



J r- ' , ' 



VOL. IV 2 A 



