140 A NATURALIST IN BORNEO 



to resemble petals, as does Idolum diabolicum. Natural 

 selection has gone, if not a step further, at least along 

 a different line, and has produced an insect that from 

 every aspect and in every detail is so flower-like that 

 warning attitudes and protective colouring of one sur- 

 face in contradistinction to an alluring colour of another 

 are lost in the effort to attain perfection along other 

 lines. 



Some Mantidce supplement their warning displays 

 by making a hissing or rustling sound, and many of 

 those that show no brilliantly coloured parts of the 

 body or its appendages produce the same sound. The 

 late Professor Wood-Mason 1 was the first to draw 

 attention to this stridulating habit in the Mantidce, and 

 other observers, among whom I may include myself, 

 have confirmed his observations. The sound is pro- 

 duced by the friction of the fore-edges of the two 

 wing-covers against the legs or abdomen. According 

 to Captain Williams, 2 when Gongylus gongylodes assumes 

 a threatening posture the wing-covers are slightly raised 

 and spread outwards and downwards, so that their fore- 

 edges come into contact with the thighs of the hind 

 pair of legs ; the insect then sways from side to side, 

 thus causing the edges of the wing-covers to scrape 

 against the thighs. On examining these edges it is seen 

 that they are serrated. Wood-Mason supposed that the 

 sound was produced by the wing-covers scraping against 

 the abdomen, but it is difficult to see how its soft and 

 rounded sides could act as a scraper on the rasp of the 

 wing-covers. He figures the edge of the wing-cover in 



1 Trans. Ent. Soc., 1878, pp. 263-7. 



3 Ibid., 1904, p. 129. See also p. 128 for an account of further 

 details in the intimidating attitude. E. B. P. 



