COLOUKATION OF INSECTS 



By THOMAS P. LUCAS, M.R.C.S.E., 



L.M. AND L.R.C.P.E., L.S.A., ETC. 



[Read before the Royal Society of Queemland, July 7, 1895.] 



Colour in insects is believed to be produced by the sunlight. 

 Various pigments appear to absorb certain rays of light, but to 

 be unable to absorb other rays. The absorption of certain rays 

 is said to mean the disappearance of ethereal vibrations at a 

 certain speed. White is supposed to be caused by irregular 

 reflection of the vibrations, and thus a greater distribution of 

 light. This irregular reflection is believed to be produced by 

 thin plates. 



Again, heat and cold appear to affect the colours. Black 

 and dark browns readily absorb heat and readily part with it ; 

 white more slowly and with difficulty absorbs heat, but slowly 

 parts with it. As witness, black and white clothes. Hence the 

 Arctic insects are largely or altogether dark coloured, to 

 snatch, as it were, every sun's ray possible for their short 

 existence. Northern birds, on the contrary, become white, so 

 as to keep the heat of the body in as slow a radiation as possible. 



Dr. Standfuss, of Zurich, experimented on a large number 

 of chrysalides of the Painted Lady and Tortoiseshell butterflies. 

 He found that by submitting these pups to a refrigerator atmos- 

 phere for 23 days, and then to normal temperature for another 

 12 days, that the emerging butterflies had the black colouration 

 very largely extended and deepened, and that the red colour was 

 faded and speckled over with black scales. In a word, under 

 the conditions of cold, the butterfly, in being dressed in blacky 

 was being prepared for a cold climate existence. 



