1896. 



HOW AND WHY SCORPIONS HISS. 



21 



lodged between the basal segments of the pincers and of the first pair 

 of legs. No doubt, too, a rustling sound is produced by the waving 

 of the pincers and the consequent friction between the adjacent 

 surfaces of these two segments. But in this case the notes or keys 

 are situated upon the base of the first leg (Fig. 3, A) and the scraper 

 upon the base of the pincer (Fig. 3, B). The arrangement is, conse- 

 quently, exactl)^ the opposite of that which obtains in Wood-Mason's 

 instrument. The position, moreover, of the stridulating areas upon 

 the respective segments is also different, the area upon the coxa of the 

 first leg being situated, not upon the main part of the segment, but 

 upon its maxillary process (see Fig. 3, B), and that upon the coxa of 

 the pincer being moved a corresponding distance to the front (Fig. 3, A). 

 The latter is thickly studded with minute spicules, and the former 

 much more sparsely with notes, smaller than those that occur in the 

 Indian species, but like them in origin and essential structure, being 

 evidently nothing but hairs expanded at the base and bent over at the 

 distal end. The form of these notes in the West African Scorpio 





Fig. 3. — Stridulating Organ of African Scorpion, Scorpio africanus. 



A, Coxa of pincer with rasp, x. B, Coxa of first leg with keyboard, z, on its 



maxillary process. C, Portion of keyboard enlarged to show the notes. 



africanus is shown in Fig. 3, C, but in some of the other species the 

 terminal part is longer and thinner. 



The scorpions possessing this organ are distributed in equatorial 

 Africa from Senegambia to the Congo on the west, and from 

 Abyssinia and Somaliland to Lake Nyassa on the east. The 

 Saharan region to the north of this area is occupied by the allied 

 genus Heterometrns ; but in this form no stridulator has been detected. 

 Ranging, however, over the whole of S. Africa to the south of the 

 area occupied by Scorpio, occurs the genus Opisthophthalmus, of which 

 most of the species possess a well-developed sound-producing organ 

 totally different both in structure and position from those that have 

 hitherto been discussed. The discovery of this organ was due to a 

 lucky chance. In the course of a correspondence with Mr. G. A. K. 

 Marshall, who has spent some years both in Natal and in Mashuna- 

 land, and has proved a most valued contributor to the national 

 collection, my interest was aroused by some casual remark of his 

 touching the stridulation of Solpuga and of scorpions, and, in reply to 

 a question on the latter point, he wrote as follows : — "With reference 

 to your inquiry as to the ' hissing ' of scorpions, I have often heard 



