Superfamily Avicularioidea 



vertically above the surface o. tne ground lor a considerable 

 distance against the side of the tree (Fig. 228). 



In the case of the web of an adult spider the portion above 

 the ground measures nearly or quite one foot in length and from 

 one half to three fourths of an inch in width. The part below the 

 surface of the ground is shorter; in the specimens that I have 

 taken, it measures from four to six inches in length. 



The outer surface of the purse-web is always protectively 

 coloured to a considerable extent. The colour varies from a light 

 gray to a very dark brown, almost black, corresponding to the 

 colour of the bark of the tree against which the tube is built. 

 The colour is due to a coat made of minute bits of bark, lichens, 

 and moss, which are evidently collected by the spider from the 

 trunk of the tree and fastened to the surface of the web. In the 

 case of a web built by a spider that 1 kept in confinement, the 

 web was partly covered with grains of sand taken from the 

 soil in the breeding cage, and there are usually grains of sand 

 on the webs built under natural conditions. 



Notwithstanding their colouring, the tubes are easily seen 

 when one has learned their appearance. They look like a dead 

 stick or a section of a climbing vine; but present a very char- 

 acteristic appearance, owing to their being perfectly straight. 

 This is well shown in Fig. 204 which is from a photograph of 

 of a tree trunk bearing both a purse-web and a vine. 



The purse-web is attached to the surface of the tree only by 

 its upper extremity, where it is flattened and somewhat expanded 

 into bands of threads by which it is fastened to the tree. Between 

 this point of attachment and its base, where it is firmly anchored 

 in the ground, it is stretched like a fiddle-string. The result 

 is that the walking of an insect over it causes it to vibrate; and 

 thus the presence of the insect is revealed to the waiting spider, 

 who waits in the tube below the surface of the ground with its 

 head upward ready to rush up the tube. 



When the tube is disturbed by the passage of an insect over 

 it, the spider rushes to the point where the insect is, and biting 

 through the web, captures it. The web is then slit and the insect 

 pulled inside the tube. After the spider has sucked its prey dry, 

 the remnant is thrown out, the slit is repaired, and the spider 

 waits for another victim. 



As a rule one finds only a single web ot an adult spider on a 



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