232 Charles Darwin. 



nal of Researches," etc., p. 381.) He has written 

 on the phosphorescence of fire-flies, and on the 

 habits of the larva of one of them Lamphyris occi- 

 dentalis. (Ibid., pp. 29, 30.) He discussed the food- 

 habits of stercovorous beetles, with reference to the 

 origination of a new habit and the power of adapta- 

 tion to new conditions. (Ibid., p. 490, note.) 



At Port St. Julian, Patagonia, he found a species 

 of Tabanus extremely common, and remarks : " We 

 here have the puzzle that so frequently occurs in 

 the case of mosquitoes on the blood of what do 

 these insects commonly feed ? The guanaco is 

 nearly the only warm-blooded quadruped, and is 

 found in quite inconsiderable numbers compared 

 with the multitude of flies." He has discussed the 

 question of hibernation of insects, and shown that it 

 is governed by the usual climate of a district, and 

 not by absolute temperature. (Ibid., pp. 98, 99.) He 

 gave the first true explanation of the springing 

 power of the Elaterida when laid on their backs, 

 showing how much depended on the elasticity of 

 the sternal spine. (Ibid., p. 31.) He was the first, I 

 believe, to record the exceptional powers of running 

 and of making sound, in a butterfly, viz., Ageronia 

 feronia of Brazil. 



In his most famous work he lays stress particu- 

 larly on the following facts and generalisations, for 

 which he draws from insects : the individual differ- 

 ences in important characters ; the remarkable man- 

 ner in which individuals of the same brood often 

 differ, dimorphism and trimorphism being only the 

 extreme exaggeration of this fact ; the difficulty of 



