Strididating-organ in. Scorpions. 57 



exactly similar in structure to that of Palamnceus, although 

 the rasp and the vibratile bristles occur upon different 

 segments of the chelas and legs of the first pair in the two 

 genera. What is believed to be a stridulating-organ has also 

 been found in certain South-African species of the genus 

 Parabuthus, which belongs to a totally different family, 

 namely, the Buthidse. Unfortunately in this instance there 

 is no proof, based upon human perception of the sound emitted 

 by the living animal, that the function of the organ described 

 has been correctly interpreted. The tenability of the suppo- 

 sition, however, is justified by the structure of the organ and 

 by the distinctly audible stridulation it can be made to yield, 

 when the appropriate movements, all capable of being per- 

 formed by the animal itself, are induced by artificial means 

 on a freshly killed or alcohol-preserved specimen. 



In the Pandinidse the stiidulating-organs have been deve- 

 loped in connexion with the anterior appendages. In Opisth- 

 ophthalmus it consists of large foliaceous bristles on the 

 inner (preaxial) surface of the basal segment of the cheli- 

 cerse, and the sound given out by the rubbing of these 

 appendages together is in many cases supplemented by the 

 sound produced by the catching of certain short, erect, stiff 

 bristles on the dorsal side of this segment against the anterior 

 edge of the carapace as the appendages are forcibly withdrawn 

 beneath it. 



In Pandinus and Palamnceus it lies between the basal 

 segments of the appendages of the third and fourth pairs, 

 commonly called the chelse and first pair of legs, and consists 

 of a finely papillate area jmd an area beset with short erect 

 bristles exactly like those that are found upon the upperside 

 of the basal segment of the chelicerge in Opisthophthalmus * '. 



In Parabuthus what is supposed to be a stridulating-organ 

 is totally different both in structure and position. It is a 

 finely granular or transversely ridged area upon the dorsal 

 side of the first and second segments of the tail, possibly also 

 upon that of the last tergal plate of the abdomen, and the 

 stridulation above mentioned can be artificially produced by 

 scraping the point of the sting over the roughened field in 

 question f. A fairly similar but less differentiated system of 

 granules, probably subserving the same end, is found upon 

 the first segment of the tail in certain black North-African 

 species of Puthus, namely, the Egyptian P. bicolor and the 

 Algerian P. ameas J. 



* See Pocock, Nat. Science, ix. pp. 17-25 (1896). 

 t Pocock, Proc. Zool. Soc, March 1902, pp. 222-224. 

 X Pocock, Ann. & Mag. Nat. Hist. (7) x. p. 374 (1902). 



