152 ME. T. M. CAMPBELL ON SUPPOSED 



On supposed Stridulating-Organs of Steatoda guttata, "Wider., and 

 Linyphia tenebricola, Wider. By F. Mattle Campbell, 

 F.L.S., F.Z.S., F.R.M.S. 



[Eead June 17, 1880.] 



Phoeessor Westeing (Naturhist. Tidsskrift, vol. iv. 1842-44, 

 p. 359, and vol. ii. 184G-1849, p. 342, and 'Aranese SuecicsB ') 

 discovered stridulating-organs in the following Spiders, viz. : — 

 Assagena pJialerata, Panz., Theridion hamatum, C. Koch, Steatoda 

 bipunctata, Linn., S. castanea, Clk., S. albomaculata, De Geer, and 

 S. guttata, "Wider. In 'Araneae Suecicse ' (1862) Prof. "Westring 

 writes of the Assagena phalerata (p. 175) " Pemina organis iis 

 caret; " but does not mention the female of the other species as 

 not possessing the stridulating-apparatus. Throughout, how- 

 ever, he refers only to its presence in males, as when speaking 

 of the male Steatoda bipunctata, he adds : — " hie sexus similiter 

 ac S Th. serratipedis, hamati, castanei, guttati et albomaculati stri- 

 dere potest. Mas descriptus post captivitatem minus libenter 

 sonum reddit, quare, si hunc audire velles, animalculum statim 

 ut capitur inter digitos ad aures est tenendum " *. Mr. Darwin 

 (' Descent of Man,' 2nd ed. p. 273) and Professor "Wood-Mason 

 (Trans. Ent.Soc. 1877, p. 282), apparently quoting "Westring, state 

 that 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 could be found in the 

 females." The Rev. O. P. Cambridge (' Spiders of Dorset,' vol. i.) 

 refers to these organs as a distinction of species in Assagena plia- 

 lerata, Panz., Steatoda bipunctata, Linn., S. guttata, Wider., and 

 S. sticta, Cambr. He describes certain of them as possessing, in 

 "the fore extremity of the abdomen, a sort of socket, serrated or 

 denticulated on its upper edge ; and into this the hinder extremity 

 of the cephalothorax fits." 



I am indebted to the last-named araneologist for specimens of 

 male and female of Steatoda guttata, "Wider., and 8. bipunctata, 

 Linn. In the male of the former the socket is a complete ring 

 with some strong chitinous spurs on the inside of its external 

 edge (fig. 1, A), which is also roughly serrated. That of the female 

 is divided into two parts, the inferior being the smallest, while 

 the superior, as in the male, is the deepest. In the female 

 * I have had no experience of this. 



