350 



ARACHNIDA ARANEAE 



not belong to the Epeiridae but to the cribellate Uloboridae, but 

 its defective orb -web is so curious that it deserves a special 

 mention. A single foundation -line is laid down, and from it 



four radii are drawn 

 and are connected 

 with cross lines, the 

 snare constituting 

 about one -sixth of 

 a circle. From the 

 centre of the incom- 

 plete circle a thread 

 proceeds to some 

 more or less distant 

 object, and on this 

 the spider takes up 

 its position, inverted, 

 and hauls in the line 

 till the snare is taut. 

 When the trembling 



FK;. 191. A, Snare of //y^wCes cva<ws ; B, enlarged 



view of the Spider, showing the "slack" of the 



hauled-in line. (After Einerton. ) 



of the line shows the 

 spider that an insect has struck the net, it lets go with its fore 

 legs, and the web, springing back to its normal position, entangles 

 the intruder more thoroughly by its vibrations. When large 

 insects are in question the spider has been observed to " spring " 

 the net several times in succession. H. cafatfws is common in 

 the pine woods of Pennsylvania, but the only English species, 

 H. jparacfcwMS, is extremely rare. 



A remarkable spider has been discovered in Texas by 

 M'Cook, which, after building a horizontal orb-web, converts it 

 subsequently into a dome (Fig. 192) of exceedingly perfect form. 

 It is named Epeira basilica, and has been the object of careful study 

 by Dr. Marx, who observed the whole process of web-construction. 

 Threads are attached at various points on the upper surface of 

 the horizontal wheel, the central portion of which is gradually 

 pulled up until the height of the dome is nearly equal to the 

 diameter of its base. But the snare of this spider does not 

 consist of the dome alone. A sheet of irregular lines is stretched 

 below, while above there is a maze of threads in the form of a 

 pyramid. Several other Orb-weavers, as, for instance, E. laly- 

 rinthea and E. triaranea, supplement their typical webs by an 



