300 



THE DESCENT OF MAN. 



segment, and are scraped by ridges on the femora.'" In certain 

 Curculionidee and Carabidse," the parts are completely reversed in 

 position, for the rasps are seated on the inferior surface of the 

 elytra, near their apices, or along their outer margins, and the 

 edges of the abdominal segments serve as the scrapers. In Pelo- 

 bius Hermanni (one of Dytlscidse or water-beetles) a strong ridge 

 runs parallel and near to the sutural margin of the elytra, and is 

 crossed by ribs, coarse in the middle part, but becoming gradually 

 finer at both ends, especially at the upper end; when this insect is 

 held under water or in the air a stridulating noise is produced 

 by the extreme horny margin of the abdomen being scraped 

 against the rasps. In a great number of long-horned beetles 

 (Longicornia) the organs are situated quite otherwise, the rasp 

 being on the meso-thorax, which is rubbed against the pro-thorax; 

 Landois counted 23S very fine ribs on the rasp 

 f of Cerambyx heros. 



Many Lamellicorns have the power of stridu- 

 lating, and the organs differ greatly in position. 

 Some species stridulate very loudly, so that 

 when Mr. F. Smith caught a Trox sabulosus, 

 a gamekeeper, who stood by, thought he had 

 caught a mouse; but I failed to discover the 

 proper organs in this beetle. In Geotrupes and 

 Typhceus a narrow ridge runs obliquely across 

 (r. fig. 26) the coxa of each hind-leg (having in 

 G. stercorarius 84 ribs), which is scraped by a 

 specially projecting part of one of the abdominal 

 segments. In the nearly allied Copris lunaris, 

 an excessively narrow fine rasp runs along the 

 sutural margin of the elytra, with another short 

 rasp near the basal outer margin; but in some 

 other Coprini the rasp is seated, according to 

 Leconte,'' on the dorsal surface of the abdomen. 

 In Oryctes it is seated on the pro-pygidium ; and, 

 according to the same entomologist, in some 

 other Dynastinl, on the under surface of the elytra. Lastly, West- 



Fig. 26. Hind- 

 leg- ot Geo- 

 trupes stercor- 

 arius (from 

 Landois). 



r. Rasp. c. Coxa. 

 f. Femur, t. 

 Tibia tr. Tarsi. 



™ Schiodte, translated in 'Annals and Magr. of Nat. Hist.' vol. xx. 

 1867, p. 37. 



" Westring has described (Kroyer. 'Naturhist. Tidskrlft,' B. ii. 1848- 

 49, p. 334) the stridulating organs in these two, as well as in other 

 families. In the Carabidae I have examined Elaphrus uliginosus and 

 Blethisa multipunctata, sent to m© by Mr. Crotch. In Blethisa the 

 transverse ridges on the furrowed border of the abdominal segment 

 do not, as far as I could judge, come into play in scraping the rasps 

 on the elytra. 



™ I am indebted to Mr. Walsh, of Illinois, for having sent me ex- 

 tracts from Leconte's 'Introduction to Entomology,' pp. 101, 143. 



