595.4 319 



IV 

 The Smallest of Stridulatiiig Spiders 



~\ /TANY readers of Natural Science will doubtless reiuendjer Mr 

 -^-^ I'ocock's interesting^ paper, published some three years ago,^ 

 on " Musical Boxes in Spiders." In that paper Mr Pocock sum- 

 marised our knowledge of the various organs which, in spiders, are 

 specially adapted for producing sound. In all cases the sound or 

 stridulation is due to the scraping of sharp spines on roughened 

 surfaces, or on a series of ridges, or on stiff, thickened hairs ; but 

 the stridulating-organ may be developed in very different parts of 

 the spider's Ijody. For example, we may find : — 



1, " AVestring's organ" — A semi-circle of teeth on the forward 

 part of the abdomen, scraping a set of ridges on the 

 hinder part of the carapace. (Males of Asaycna, Pcclanos- 

 tcthus, and some other Theridiidae.) 



'1. " Campbell's organ " — A set of ridges on the femur of the 

 palp, scraping a similar set on the outer surface of the 

 mandible. (Males of Leptyphantcs ; imperfect in female.) 



o. " Simon's organ "—A set of spines on the femur of the palp, 

 scraping a set of ridges on the outer surface of the mandible. 

 (Both sexes of Thomisoidcs.) A similar organ, in which, 

 however, the femur of the palp bears only a single strong 

 spine, has been since discovered in both sexes of Scytodes 

 by Mr F. Pickard- Cambridge.^ 



4. " Wood-Mason's organ " — A set of stout spines on the man- 

 dible, scraping a series of club-like rods (thickened hairs) 

 on the coxa (basal segment) of the palp. (Both sexes of 

 Poccilotheria, Selenocosmia, &c.) This organ has recently 

 been re-discovered by Mr Pocock (it had been described 

 in 1867 by Blackwall, who was, however, ignorant of 

 its purpose) in the South American Trcchona zehrata? 

 Mr Pocock has also foiuid the organ in the Australian 

 Idiommata hlackwcdlii,^ while it has been described and 

 figured iu another Australian species — Phlogius crassipes, 

 by Professor Baldwin Spencer.^ A closely similar organ is 

 stated by Mr Pocock to occur in species of the Ethiopian 



1 Vol. vi., 1895, pp. 44-50. 



- Ann. Mag. Nat. Hist. (6), vol. xvi., p. .371. 



^ Ann. Maq. Nat. Hist. (6), vol. xvii., pp. 177-9. 



* Op. cit. (G), vol. xvi., p. 225. 



^ Rep. Horn Expcd., vol. ii. ; Zoology, pp. 412-14. [See Nature, vol. li., p. 43S.] 



