No. 1.] 



SEXUAL SELECTION IN SPIDERS- 



29 



in the male, while in the female they are short, weak and with- 

 out teeth."^ He also speaks of the entirely different colors of 

 the male and female falces of the same species. Not infre- 

 quently there are two forms among the 

 males of a species, one Math long and mod- 

 ified falces, and another having them 

 short, and more like those of the female. 

 In Fensacola signata, an Attus from Guate- 

 mala, we have two such forms. To quote | 

 from a former paper of our own : " In the 

 first, which is a little the larger, the falces 

 are more than twice as long as the face, lafo^^if'r^fmertonf Left-" 



Till I !• X ii 1 J hand figure, falx of male: 



slightly retreating, narrow at the base and right-hand figure, taix of 

 extremity, but dilated in the middle when 

 looked at from in front. Near the anterior inner edge, in the 

 middle, is a strong apophysis or spine in each falx, which 

 reaches nearly to the end of the fang ; fang long and slightly 

 bent. In the second form the falces are relatively shorter, and 

 are but very little dilated 

 in the middle, so that the 

 curve on the inner edge is 

 not marked, and the spine 

 is less than half as long as 

 in the first form. We find 

 others intermediate be- 

 tween these two extremes."' 

 Canestrini also refers to the 

 existence of two male 



fnr-iYic Qiirl AY-nl«in« til Am ^^^- 7- — Tetragnatha straminea (from Emer- 

 lornib, anu expiaint. uneiu t^u) Left-hand figure, falx of male; right-hand 

 1 ji ... ii J figure, falx of female. 



by the supposition tliat we 



here see these secondary sexual characteristics, as it were, in 



process of development.* 



Another curious modification is found in Icius cornutus, 



1 Caratteri sessuali secondarii degli, Araclmidi, Atti della See. Vento— Tren- 

 tina di Sc. Nat. Padova, I, Fasc. 3, 1873. 

 2ioc. cit. 



3 On Some. New (ienera and Species of Attidm, G. W. and E. G. Peokham, Proc. 

 Nat. mst. Soo. of Wisconsin, 1S87, p. 84. ^ , „ , ,,. . 



4 This occurs in Phikeus miUtarl.i, Icius palmarum. and ZygobaUus oettim. 

 Canestrini mentions the genera Linyphia, Theridium and Dysdera, 



