i 9 o AMERICAN SPIDERS 



attached to a near-by leaf; inside the retreat lies the spider, hold- 

 ing the trap line stretched to the center of the orb. Spiders that use 

 these trap lines first swing to the center of the web, then directly 

 toward the point where the prey is entangled. 



A great many of our largest orb web weavers spin a complete 

 orb and communicate with it by means of a trap line stretched 

 from a retreat of folded leaves. Typical is the common shamrock 

 spider, Aranea trifolium (Plates 7 and 18). This animal, often more 

 than a half inch long, has an evenly rounded, white to pink abdomen, 

 usually marked above with a three-lobed spot resembling a sham- 

 rock. Its carapace is banded with brown, and its legs are conspicu- 

 ously ringed with white and brown. The male is only about one 

 fifth of an inch long. Even more stikingly colored is the related 

 round-shouldered weaver, Aranea raji, which, common over most 

 of the United States and well known in Europe, has a bright orange 

 body and an abdomen marked by contrasting darker lines of an 

 indistinct folium. 



Larger even than the round-shouldered orb weavers are some 

 that have a bulky abdomen produced into prominent basal humps. 

 These gray or brown spiders sit at the side of their complete orb 

 webs in a crevice, under chips of wood, under bark, or in a more 

 formal leafy retreat. One of the most familiar is Aranea gemmoides 

 (Plate XXII), which is widely distributed from Nebraska westward. 

 It varies from pale yellow to near black. The commonest eastern 

 representative is Aranea nordmanni, a somewhat smaller and darker 

 spider, with folium on the abdomen, which is thought to be similar 

 to a European species. 



Included among the typical orb weavers is one small group that 

 has repudiated the orb web in favor of a distinctive and extraordi- 

 nary method of capturing insects. These are the bolas spiders of 

 the genus Mastophora (Plates III and XXIII), fat creatures of above- 

 average size, whose bodies are ornamented in a most grotesque 

 manner. The carapace is bedecked with sharp, branched crests or 

 horns, and set with many small, rounded projections; the volumi- 

 nous abdomen is lined and wrinkled and surmounted with rounded 

 humps. These bizarre specializations, reminiscent of similar orna- 

 mentation in the dinosaurs and other groups of animals, are not 

 known to play an important part in the life of the spiders. 



The hunting site of female Mastophora is usually the outer 

 branch of a shrub or tree, most often high off the ground. On this 

 the spider hangs in plain sight. Mementoes of her previous activities 

 are numerous silken lines that soon form a thin coating over the 



