CHAPTER XII. 



THE RAY SPIDER AND HER SNARE : ACTINIC ORB. 



I. 



Ix the vicinity of Philadoljiliia, 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 

 Positio ^ 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. ^ I then intimated that it would j)rob- 

 ably be assigned to a new genus, and sub.sequently in a verbal communi- 

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

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

 epeira.^ 



Subserpient investigation led me to believe that the spider belongs to 

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

 European form Theridiosoma gemmosum of L. Koch.* This genus has 

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

 ground of structure apjjears to be at least equally related to the Epeiroids. 

 Count Keyserling, however, in his extended and admirable monograph 

 of the American spiders,^ retains the species among the Retitelarite, where 

 it had previously been placed. 



But the spinningwork shows conclusively that it must be placed with 

 the Orbitelariaj. To that position, therefore, I have assigned it," 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 Actinse.' The systematic position and relations of the 



' Proceeflings Academy Natural Sciences of PliiUKlelphia, 1881, pages 103-1 "5. 



2 Trans. Conn. Acad., S'ol. VI., 1884, page 320. 



^ Rev. O. Pickard-Caml iridge. Theridiosoma argenteolimi : Annals and Magazine of 

 Xatural History, 1879, page 193. 



■* Theridium gemmosum : Verzeichniss der bei Xurnbei-g beob. Arten, page 69. 



' Die .Spinnen Amerikas : Theridiidw, von Graf E. Keyserling, Zweiter Band, page 218. 



'' Proceed. Acad. Xat. Sci., Phila., 1889, page 180. " Xote on the True Systematic Position 

 of the Ray Spider." 



' Actis, a/iT/f, a ray. 



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