o 



20 NATURAL SCIENCE [May 



genus Harpadira} He believes, therefore, that it must 

 have been independently developed in various groups of 

 the Aviculariid spiders. 

 5. " Pocock's organ " — A set of spines on the coxa of the palp, 

 scraping a series of club-like rods on the mandible. 

 (Both sexes of Phormingochilus, &c.) 



Since Mr Pocock published his paper in Natural Science, he has 

 described two new stridulating organs in spiders. It may be of 

 interest to summarise their structure : — 



6. A large heart-shaped tooth on the anterior sclerite of the 



pedicel (narrow " stalk " between carapace and abdomen) 

 scrapes a set of six horny, arched ridges situated in a 

 cave-like hollow beneath the base of the abdomen. (Males 

 of the New Zealand agelenid Camhridgea antiiJodiana}) 



7. A set of spines on the hinder surface of the coxa of the 



palp plays on a series of modified hairs on the front 

 surface of the coxa and trochanter of the first walking- 

 leg. (Both sexes of Eumcnophorus and allied Ethiopian 

 aviculariids.^) 



Having briefly reviewed our knowledge of these organs, it is 

 now my privilege to give an account of a very interesting " musical 

 box," whose construction differs widely from that of any of the 

 above : — 



8. The inner hinder corner of the coxa in the fourth pair of 

 legs is drawn out into a sharp point, scraping over the 

 surface of the " lung-book " cover, which is traversed 

 by a complicated series of ridges and furrows. (Male of 

 Entelecara hroccha.) 



The spiders on whose sound-producing organs Mr Pocock 

 has specially worked, are the Aviculariidae, some of the 

 largest members of the order. The species in which I have 

 observed the organ whose structure is summarised above, is, on the 

 other hand, one of the tiniest of spiders ; measuring only about 

 1| mm. in length. J^ov some years past I have been working up 

 the arachnid fauna of Ireland, and a number of friends have been 

 good enough to collect material for me in their rambles in different 

 parts of the country. One of the most energetic of these is Mr 

 11. Welch, of Belfast (whose geological photographs must be familiar 

 to many readers of Natural Science). And it was he who found in 

 October last, on the summit of Slieve Donard, the highest point of 

 the Mourne Mountains, some 2790 feet above sea-level, the little 



1 Proc. Zool. Soc, Lond., 1897, p. 771. 



2 Ann. Mag. Nat. Hid. (6), vol.. xvi., p. 230. 

 '■^ Proc. Zool. Soc, Lund., 1897, p. 744. 



