LITERATURE 203 



in fact, seem that in the stick insect the hypodermal cells are 

 virtually unspecialised chromatophores. 



(g) Mottram and Cockayne (1920) and Cockayne (1924) have 

 shown that fluorescence is a common colour property among 

 Lepidoptera. By using a quartz mercury vapour lamp, whose 

 light was allowed to pass through a sheet of a special kind of black 

 glass, which is opaque to white light, a beam of invisible ultra- 

 violet radiation was obtained. When this beam is directed upon 

 insects in a dark room any fluorescence present reveals itself. It 

 was found that the phenomenon is widely spread among species 

 that are whitish or yellow, or have markings of such colour upon 

 their wings. The fluorescent colours vary very greatly, being 

 pale blue in many Geometridae, dull violet among Pieridse, bright 

 yellow in some Arctiidse, and bright green in the Danainse. The 

 phenomenon may be common to both sexes as in Geometridae, 

 while many Papilionidse have fluorescent males and non-fluorescent 

 females. It is interesting to speculate with regard to the possible 

 relationships of fluorescent pigments to one another, and this 

 property may prove to be a useful index of affinity as regards 

 chemical constitution. Whether fluorescence is of any functional 

 importance in the lives of insects whose colours exhibit the 

 phenomenon, or is solely an incidental feature, is problematical. 



Literature 



Atzler, 1930. Zeits. vergl. Physiol., XIII., 505. 

 Brecher, 1917. Arch. f. Entw. Mech., XLIIL, 88. 



1921. Ibid., XLVIIL, 46. 



1922. Ibid., L., 209. 



1923. Zeit. Indukt. Abstammslehre, XXX., 291. 



1924. Arch.f. FaUw. Mech., CO., 501. 



1925. Zeits. vergl. Physiol., II., 691. 

 Brindley, 1929. Trans. Ent. Soc. London, LXXVIL, 5. 

 Cockayne, 1924. Ibid., LXXII., 1. 



Durken, 1923. Arch.f. Mikros. Anal., XCIX., 222. 

 Faure, 1932. Bull. Ent. Res., XXIII., 334. 

 Fulton, 1922. Quart. Journ. Mic. ScL, LXVL, 339. 

 Gerould, 1921. Journ. Exp. ZooL, XXXIV., 385. 



1926. Ibid., XLIIL, 413. 



1927. Quart. Rev. Biol., II., 58. 

 Giersberg, 1928. Zeits. vergl. Physiol., VII., 657 

 Glaser, 1917. Psyche, XXIV., 30. 

 Harrison, 1928. Proc. Roy. Soc, B, CIL, 338. 



1928a. Ibid., 347. 



