CHAPTEE XII. 

 THE RAY SPIDER AND HER SNARE : ACTINIC ORB. 



I. 



Ix the vicinity of Philadelphia, June 14th, 1881, I found a number 

 of spiders grouped not far from each other on orbicular webs, which 

 proved to be of a type previously unknown, and which I called the Ac- 

 tinic or Ray formed orbweb. At the time of my discovery 

 p ... I considered the spider new to science, and gave it the name 

 of Epeira radiosa in a paper containing a careful and detailed 

 description of its spinning habit. 1 I then intimated that it would prob- 

 ably be assigned to a new genus, and subsequently in a verbal communi- 

 cation proposed for it "the name Actis radiosa. Emerton, in his monograph 

 of the New England Epeiridse, created for the spider the genus Micro- 

 epeira. 2 



Subsequent investigation led me to believe that the spider belongs to 

 Cambridge's genus Theridiosoma, 3 and probably is identical with the 

 European form Theridiosoma gemrnosum of L. Koch. 4 This genus has 

 marked resemblances to Epeira, as Cambridge himself allows; and on the 

 ground of structure appears to be at least equally related to the Epe'iroids. 

 Count Keyserling, however, in his extended and admirable monograph 

 of the American spiders, 6 retains Jthe species among the Retitelariae, where 

 it had previously been placed. 



But the spinningwork shows conclusively that it must be placed with 

 the Orbitelaria3. To that position, therefore, I have assigned it, 6 and it 

 becomes necessary to transfer the genus Theridiosoma from the Retitelariae 

 to the Orbitelarise, and to make for it a new family, for which I have 

 proposed the name Actinae. 7 The systematic position and relations of the 



1 Proceedings Academy Natural Sciences of Philadelphia, 1881, pages 163-175. 



2 Trans. Conn. Acad., Vol. VI., 1884, page 320. 



3 Rev. O. Pickard-Cambridge. Theridiosoma argenteolum : Annals and Magazine of 

 Natural History, 1879, page 193. 



4 Theridium gemmosum : Yerzeichniss der bei Nurnberg beob. Arten, page 69. 



5 Die Spinnen Amerikas : Theridiidse, von Graf E. Keyserling, Zweiter Band, page 218. 



6 Proceed. Acad. Nat, Sci., Phila., 1889, page 180. " Note on the True Systematic Position 

 of the Eay Spider." 



7 Actis, a*r/c, a ray. 



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