SEXUAL SELECTION 865 



the male of whicla has the left mandible much enlarged; so 

 that the mouth is greatly distorted. In another Carabidoua 

 beetle, Eurygnathus,' we have the case, unique as far as 

 known to Mr. WoUaston, of the head of the female being 

 much broader and larger, though in a variable degree, than 

 that of the male. Any number of such cases could be 

 given. They abound in the Lepidoptera: one of the most 

 extraordinary is that certain male butterflies have their 

 forelegs more or less atrophied, with the tibiae and tarsi 

 reduced to mere rudimentary knobs. The wings, also, in 

 the two sexes often differ in neuration," and sometimes 

 considerably in outline, as in the Aricoris epitus, which 

 was shown to me in the British Museum by Mr. A. Butler. 

 The' males of certain South American butterflies have tufts 

 of hair on the margins of the wings, and horny excrescences 

 on the disks of the posterior pair." In several British 

 butterflies, as shown by Mr. Wonfor, the males alone are 

 in parts clothed with peculiar scales. 



The use of the bright light of the female glow-worm 

 has been subject to much discussion. The male is feebly 

 luminous, as are the larvae and even the eggs. It has been 

 supposed by some authors that the light serves to frighten 

 away enemies, and by others to guide the male to the 

 female. At last, Mr. Belt" appears to have solved the difii- 

 culty: he finds that all the Lampyridse which he has tried 

 are highly distasteful to insectivorous mammals and birds. 

 Hence it is in accordance with Mr. Bates's view, hereafter 

 to be explained, that many insects mimic the Lampyrid^ 

 closely, in order to be mistaken for them, and thus to escape 



» "Insecta Maderensia," 1854, p. 20. 



'» B. Doubleday, "Annals and Mag. of Nat. Hist.," vol. L, 1848, p. 379. 

 I may add that the wings in certain Hymenoptera (see Shuckard, "Possorial 

 Hymenop.," 1837, pp. 39-43) differ in neuration according to sex. 



" H. W. Bates, in "Journal of Proc. Linn. Soc," vol. vi., 1862, p. 74. 

 Mr. Wonfor's observations are quoted in "Popular Science Review," 1868, 

 p. 343. 



" "The Naturalist in Nicaragua," 1874, pp. 316-320. On the phos- 

 phorescence of the eggs, see "Annals and Mag. of Nat. Hist.," Nov. 1871, 

 p. 372. 



