JSPIDSM 09 



he adds, filled him with horror and indignation/'* The Rev. 

 0. P. Cambridget accounts in the following manner for 

 the extreme smallness of the male in the genus Nephila: 

 ^' 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 favor 

 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, probaby 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 TheridionJ; have the power of 

 making a stridulating sound, while the females are mute. 

 The apparatus 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 AValck- 

 enaer, have declared that spiders are attracted by 

 music. From the analogy of the Orthoptera and Homop- 

 tera, to be described in the next chapter, we may feel 

 almost sure that the stridulation serves, as Westring also 

 believes, to call or to excite the female; and this is the first 

 case known to me in the ascending scale of the animal 

 kingdom of sounds emitted for this purpose. || 



* Kirby and Spence, "Introduction to Entomology," vol. i, 1818, 

 p. 280. 



t " Proc. Zoolog. Soc," 1871, p. 621. 



X TheHdion {Amgena, ^iind. ) serratipes, 4-punctatnm et guttatum; 

 see. Westring, in Krover, " Naturbist, Tidskrift," vol. iv, 1842-1848, 

 p. 349; and vol. ii, 1846-1849, p. 342. See, also, for otber sj^ecies, 

 " Araneae Suecicae," p. 184. 



Dr. H. II. van Zouteveen, in bis Dutcb translation of this work 

 (vol. i, p. 444), has collected several cases. 



I Hilgendorf, however, has lately called attention to an analogous 

 structure in some of the higher crustaceans, which seems adapted to 

 produce sound; see "Zoological Record," 1869, p. 603. 



