SPIDERS 161 



sweeping strokes of its spinnerets (Bristowe, 1954). Sometimes 

 several of these spiders live quite close together in a colony. 



Web-building spiders usually construct a retreat amongst the 

 vegetation from which their snare is suspended. Vibrations of a 

 signal-thread connecting their shelter with the web enable them 

 instantly to detect the struggles of any insect that has been caught. 

 Some species are peculiar in that they show a tendency towards 

 social habits. This is apparent among a number of cribellate 

 families and an Australian species Amaurohius socialis from the 

 Jenolan Caves constructs enormous communal and densely fabri- 

 cated webs measuring as much as 12 feet in length and 4 feet in 

 width, which are inhabited by a large number of individuals. In 

 a similar way communal webs constructed by Theridion socialis and 

 Uloborus republicanus have been described. 



The spider's web is unique among animal productions in that, 

 (save one constructed by a caddis larva) it is the only trap built by 

 an animal. The web is so efficient for obtaining food that its owner 

 seldom makes use of any sense save that which the action of the 

 web demands, and the lives of web-building species are almost 

 entirely governed by responses to tactile and vibratory stimuli 

 supplemented by the development of the muscular sense. The 

 methods of construction of the various types of web have attracted 

 a great deal of attention, in particular from MacCook (1889-94), 

 Peters (1933, etc.), Tilquin (1942) and Wiehle. To review all this 

 work would be beyond the scope of the present volume, but 

 fortunately much of it has been summarised recently by Savory 

 (1952), from whose book further details can be obtained. Bristowe 

 (1930) has suggested that the origin of webs lies in the use of silk 

 as a covering for spiders' eggs which were then guarded by the 

 mother and from which random threads radiated but Savory thinks 

 that they have resulted from an accumulation of drag lines, laid 

 down by ancestral hunting spiders when their prey was captured 

 and which later gave the spiders warning of other insects passing by. 



The typical procedure in the construction of an orb web is the 

 construction of a frame followed by that of the radii. A few spirals 

 around the centre hold the radii in place while the spider travels 

 outwards spinning a widely spaced temporary spiral. Finally the 

 spinning of viscid spirals starts at the outside and works inwards 



L S.S.C.M. 



