595.4 319 



IV 



The Smallest of Stridiilatiiig Spiders 



MANY readers of Natural Science will doubtless reiueinber Mr 

 Pocock'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 body. For example, we may find : — 



1. " Westring'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 Asae/ena, Pcclanos- 

 tcthua, and some other Theridiidae.) 



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



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

 mandil)le. (Males of Lejjtyph antes ; 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 Thoriiisoiclcs.) 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 Se//todcs 

 by Mr F. I'ickard-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 

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

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

 in 18G7 by Blackwall, who was, however, ignorant of 

 its purpose) in the South American Trcchona zebrcda? 

 Mr Pocock has also found the organ in the Australian 

 Idiommata hJaekwedlii,^ while it has been described and 

 figured in 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. Hid. (0), vol. xvi., p. -371. 



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



^ Op. eit. (6), vol. xvi., p. 225. 



^' Rep. Horn ExpecL, vol. ii. ; Zoology, pp. 412-14. [See Nature, vol. li., p. 438.] 



