84 PEOKIIAM. [Vol. 1, 



On the bark these marks are, of course, irregular, while on the 

 spider they form a pattern made up of straight and curved 

 lines and dots, the legs being silvery, barred with blackish. 



Another little Theridion that is found on birch bark has 

 the same colors arranged a little differently. The abdomen 

 above has a large and peculiarly irregular black patch, which 

 shades off into mottled brown and black on the sides and below. 

 The cephalothorax has stripes of brown and black, and the legs 

 are barred with light and dark brown. 



Spiders that live upon walls, fences, tree trunks, or on the 

 ground harmonize in color with the surfaces upon which they 

 are found, being usually gray, brown or yellow, mottled with 

 black and white. This proposition is so well established* as to 

 need but few illustrations. The Therididse furnish many 

 examples, as T. murarium, a gray spider varied with black and 

 white, said by Emerton to live usually " under stones and 

 fences, where it is well concealed by its color"; and Lophocarenum 

 rostratum, a yellowish brown spider, found among leaves on the 

 ground. Among the Attidse bright sexual coloring often gains 

 the ascendancy over the protective tints, yet this family gives 

 us good examples in such species as M. familiaris and S. pulex. 



To these may be added an as yet undescribed species 

 which we discovered last season in a neighborhood that we had 

 searched thoroughly for eight summers. We found the new 

 spider in great numbers, but could only detect it by a close 

 scrutiny of the rail fences on which it lived, its color being dark 

 gray. 



Among the Lycosidte we have scores of dull-colored species 

 that live on the ground. Vinson refers to L. vulcani, which is 

 of a smoky black color and which lives in the crater of a 

 volcano, saying : "Its sinister color seems to conform to its 



* Dr. McCook says : "Spiders that nest in stables, lionses, on fences, etc., ordin- 

 arily have dusky colors harmonious with the environment." — Notes on Jielations of 

 Structure and Function to Color Changes in Spiders, Proc. Acad, of Natural Sciences 

 of Philadelphia, 1888, p. 174. See also Ce.nni sulle colorazioni e forme mimetiche utili 

 nei ragni, by Prof. P. Pavesl, in Atti d. Societa Ital. d. Scienze Naiurali, Vol. XVni, 

 1875. 



