ARANEIDA THERIDIID^. 65 



Erigon infernalls Keyserling. 



KEYSERLING, Die Spinn. Am., Therid., 11, 180, fig. 239 (Reynolds Cave, Kentucky). 

 PACKARD, Mem. Nat. Acad. Sci., iv, 1888, 58, pi. 15, fig. 33. MARX, Proc. U. S. 

 Nat. Mus., XII, 1889, 534. 



Fairly common within the cave. Twice found in pairs, a male and 

 female being under the same stone. Three times this species was found 

 with a fairly good but irregular web in an angle of the wall. It has 

 been taken in twilight as near the mouth as " 3, " but when in twilight 

 has always been found under stones and without a web. It seems more 

 at home in absolute darkness, where in every case but one it has been 

 found to have a web in an angle of the wall, under the edge of a rock 

 or in some such place. In one case two were found at an old bait which 

 had been left under a stone. It has a small web and may feed upon Dip- 

 tera, but probably also feeds upon the thysanurans and decaying organic 

 matter. It seems quite possible that this species is attracted to the bait 

 by the abundance of small flies and thysanurans which congregate there 

 rather than by the bait itself. 



This species has the dull color and retiring habits of a typical cave 

 creature. Three individuals examined show various degrees of devel- 

 opment of the eyes. In one (adult female) , the eyes were about normal 

 and the front middle eyes were about three-fourths the diameter of the 

 others; in the second (adult male) the eyes were all slightly reduced in 

 size and the front middle eyes were about two- thirds the others; while 

 in the third (adult female) all were much reduced in size and the front 

 middle eyes were very small. Keyserling's drawing, reproduced by 

 Packard (1888, plate XV, fig. 33) shows all the eyes reduced in size and 

 the front middle ones about two-thirds the diameter of the others. 



This species is not known to occur outside of caves. Taken in Twin 

 Cave at Mitchell. 



A new Theridid, probably a new genus, was taken near the mouth. 

 Mr. Nathan Banks, to whom it was sent, has not yet described it. 



The family Theridiidae includes the great majority of cave species 

 of true spiders (Araneida). This is an immense group and includes 

 many species which live in shady woods, in dense vegetation, under 

 leaves and logs, and about wells and cellars. It is not surprising that 

 such a group frequents caves and that some of its species become cave 

 inhabitants. Nine out of 16 of the true spiders of Mayfield's Cave 

 belong to this group, while of the 8 species which are permanent 

 cave residents 5 belong to this group. From other Indiana caves are 2 

 more species of this group and from other American caves are 5 more. 

 Of the total of 15 cave-inhabiting American species of this group, 7 are 



