Ohap. IX. Spiders. 273 



the fact that the males of certain species present two forms, 

 differing from each other in the size and length of their jaws ; and 

 this reminds ns of the above cases of dimorphic crustaceans. 



The male is generally much smaller than the female, sometimes 

 to an extraordinary degree, 20 and he is forced to be extremely 

 cautious in making his advances, as the female often carries her 

 coyness to a dangerous pitch. De Geer saw a male that " in the 

 u midst of his preparatory caresses was seized by the object of 

 " his attentions, enveloped by her in a web and then devoured, a 

 " sight which, as he adds, filled him with horror and indignation." 21 

 The Eev. 0. P. Cambridge 22 accounts in the following manner 

 for the extreme smallness of the male in the genus Kephila. 

 " M. Vinson gives a graphic account of the agile way in which 

 " the diminutive male escapes from the ferocity of the female, by 

 " gliding about and playing hide and seek over her body and 

 " along her gigantic limbs : in such a pursuit it is evident that 

 " the chances of escape would be in favour of the smallest males, 

 " while the larger ones would fall early victims ; thus gradually 

 " a diminutive race of males would be selected, until at last they 

 " would dwindle to the smallest possible size compatible with the 

 " exercise of their generative functions, — in fact probably to the 

 " size we now see them, i.e., so small as to be a sort of parasite 

 " upon the female, and either beneath her notice, or too agile and 

 " too small for her to catch without great difficulty." 



Westring has made the interesting discovery that the males 

 of several species of Theridion 23 have the power of making 

 a stridolating sound, whilst the females are mute. The ap- 

 paratus consists of a serrated ridge at the base of the abdomen, 

 against which the hard hinder part of the thorax is rubbed ; and 

 of this structure not a trace can be detected in the females. It 

 deserves notice that several writers, including the well-known 

 arachnologist Walckenaer, have declared that spiders are attracted 

 by music. 24 From the analogy of the Orthoptera and Homoptera, 



20 Aug. Vinson (' Aran^ides des tion to Entomology,' vol. i. 1818, 

 lies de la Reunion,' pi. vi. figs. 1 p 280. 



and 2) gives a good instance, of the 22 'Proc.Zoolog. Soc' 1871, p. 621. 



small size of the male, in Kpeira 23 The fid ion (Asagena, Sund.) 



nigra. In this species, as I may scrratipcs, 4-punctatum et gutta- 



add, the male is testaceous and the turn ; see Westring, in Kroyer, 



female black with legs banded with ' Naturhist. Tidskrift,' vol. iv. 1842- 



red. Other even more striking 1843, p. 349 ; and vol. ii. 1846- 



cases of inequality in size between 1849, p. 342. Se.e, also, for other 



the sexes have been recorded species, 'Araneaj Suecica?,' p. 184. 

 '.'Quarterly Journal of Science,' 24 Dr. H. H. van Zouteveen, in 



1868, July, p. 429); but I have his Dutch translation of this worK 



aot seen the original accounts. (vol. i. p. 444), has collected severa 



21 Kn by and Spence, ' IntrMuc- casos 



13 . - 



