THE TEMPERATURE OF INSECTS. 293 



speedy occurrence of the chemical action which brings about the 

 maturation of pollen and ova'j we cannot neglect this factor of 

 colour. The dusky mountain Argus, gathering radiant energy 

 in its wings and body on a sunny slope, at the onset of an alpine 

 storm creeps into the cover of the thick grass, where radiation 

 from its body-surface is not so rapid as in the open air ; it folds 

 its wings above its body, and this again prevents rapid radiation 

 from the vital regions so covered. If it be one of those Erebias 

 — such as E. lappona or tyndarus — which are confined to the 

 highest regions, it offers to the expanse of the outside air not 

 the dark brown of its upper surface, but the lighter grey of the 

 under side of its hind wings, which thus have a lower emissive 

 power. Again, we cannot neglect the factor of colour in deter- 

 mining the vital capacities and functions in so far as they are 

 influenced by temperature. 



My object in these remarks has been to draw attention to 

 some experiments by Prof. Bachmetjew on the temperature of 

 insects ; these experiments confirm the opinion that the effects 

 of Nature are seldom brought about by causes acting singly, but 

 by a complex interaction of many simple causes. 



The surface colour of organisms must certainly be taken into 

 account when considering their temperature relations ; there 

 appear to be suggestions in Nature that certain colours have 

 been selected as being advantageous to the animals possessing 

 them, owing to their absorptive, emissive, and reflecting powers ; 

 and this factor may have acted in common with many others, 

 known and unknown, in producing the varied effects which we 

 see and admire. 



