Superfamily Argiopoidea 



Genus THERIDIOSOMA (The-rid-i-o-so'ma) 



The abdomen is globular; the posterior median eyes are 

 slightly closer to each other than to the posterior laterals. 



The following is our best-known species; a second species, 

 T. argentatum, occurs in the South. 



The Ray-spider, Tberidiosoma radiosa (T. ra-di-o'sa). — The 

 length of the body of the female is one tenth inch; of the male, 

 one twelfth inch. The cephalothorax is cordate, truncate at 

 base, the head is much elevated. The abdomen is rounded, oval 

 and highly arched. The external reproductive organs are very 

 prominent; the epigynum of the female being large and vaulted; 

 and the bulb of the palpus of the male being very large. The 

 abdomen varies from straw-yellow to black, but all are marked 

 with many small silvery spots which give the spider a shining 

 appearance. 



The web of this spider represents a unique type. As this is 

 the only species of this subfamily whose web has been observed, 

 we are unable to say whether its pecularities are distinctively 

 characteristic of the species or are shared by other members of the 

 subfamily. 



The web was first described by Doctor McCook in 1883 and 

 no subsequent account of it has been published. But owing to 

 the common occurrence of the spider at Ithaca, N. Y., 1 have 

 had abundant opportunities for observing it. 



The spider prefers damp situations. It is most often found 

 in the vicinity of streams or in damp forests. It often makes its 

 webs on the face of a cliff over water. Although I have seen 

 large numbers of the web, I have never found one in the field 

 sufficiently well lighted and with a suitable background to enable 

 me to photograph it. The accompanying figures are from pho- 

 tographs of webs made by spiders in confinement. 



A remarkable feature of this web is that there is no hub 

 (Fig. 415). The radii converge upon a small number of lines 

 radiating from a point at or near the centre. These lines are 

 termed rays by Doctor McCook; and the entire web a ray-formed 

 web. There are usually four or five of these main divisions or 

 "rays"; there is a large free zone which occupies about one third 

 of the diameter of the web; there is no notched zone; and, in most 

 of the webs that 1 have observed, less than a dozen turns of the 



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