OF WASHINGTON. 107 



anterior legs of the male elevated on little projections. In the 

 Dictynidce the males of Dictyna have the mandibles longer than 

 the female, and bowed. In the Clubionidas a few species of 

 Clubiona have ridges on the edge of the mandibles of the male. 

 In three species of Gayenna (G. calcarata,fraterna. and pec- 

 torosd} there are spines on the posterior coxae ; these are possibly 

 of use in holding the female. In Thargalia several species have 

 horny shields at the base of the abdomen in the male. In the 

 Drassidae several species also have a horny shield at the base of 

 abdomen of the male. 



In the Dysderidas the anterior metatarsi of the male Ariadne 

 bicolor are curved and have a spine on each side. In Plectrurys 

 may be noticed a hook-like process on the anterior tibia of the 

 male, and the males of Eurypelma (Theraphosidas) also have a 

 curved hook at the same place. These projections are probably 

 of use in holding the female. The mandibles of the male of 

 Psilochoi -us pulhilus (Pholcidae) have each a spine on the front; 

 the same are found in Pholcophora americana; in the latter 

 species there is also a hump on each anterior corner of the sternum. 

 In Physocyhis gibbosus it is the female that is modified, the 

 hinder part of the cephalothorax is elevated behind into a spine. 

 The cephalothorax of the male is flat as usual in the genus. 

 These various projections on the mandibles of the Pholcidas are 

 probably of no use in righting, and probably not ornamental. 



When one considers that each of these species has several allied 

 species that exhibit no sexual structural peculiarities, it is difficult 

 to explain the cause of these structures. Many cannot be used 

 in fighting. Some Attidas, as Zygoballus, are known to fight ; 

 but there are other Attidas that also fight, and show no sexual 

 structural differences. A few of them may be ornamental. 



However, one must draw largely upon his imagination to find 

 any use for some of these structures. 



I would rather suppose that it is a part of the male inheritance 

 to be endowed with an intense nervous restlessness that some 

 times finds an expression in extreme developments of color or 

 structure. Sometimes these may be seized upon and maintained 

 by sexual selection. And. again, although they are not useful, 

 they may be maintained as outlets for the excessive vigor of the 

 male. 



This, I think, would be more plausible than that they are the 

 results of accidental variation -maintained by sexual selection. 



The next paper, " Notes on the Habits of two Cicindelidae 

 from Texas," by Mr. J. D. Mitchell, of Victoria, Texas, was 

 presented by Mr. Schwarz, who made some introductory remarks 



