56 



The Naturalist. 



are pale, sometimes simply with only two dark lines running across 

 the wings. Between the chalk and the peat they are intermediate, 

 and on the clay mud the insects are an ochreous mud colour. The 

 same takes j)lace in Thajiaos tages, and no doubt many other species, 

 if properly examined, would be found to vary according to their 

 particular habitat. As a case of that kind I might mention Polia chi 

 and the var. olivacea^ the latter being found chiefly on the dark walls 

 near the moor edges. Yet there must in some cases be some other 

 agent at work than that which we know as natural selection, for Mr. 

 Darwin has shown that the puj^a of P. Nirem will assume the colour 

 of almost anything to which it attaches itself ; and Miss Golding- 

 Bird {Ent. xi., 108) tells us that the larvae of C. nupta and Biston 

 Jiirtaria are dark or light, according to their surroundings, even when 

 kept in confinement, where no known process of natural selection 

 could operate. 



I have said that cold and shade have a tendency to produce dull, 

 indistinctly coloured specimens ; we must therefore suppose that sun 

 and warmth have the contrary effect of producing bright, distinct 

 colours, and Mr. Bond told me of an instance which seems to bear 

 out this theory remarkably well. Mr. Bond obtained eggs from an 

 ordinary female of SterrJia sacraria, and during the time he was 

 carrying them through their transformations there was scarcely any 

 sunshine at all — the dullest weather possible. The previous year Mr. 

 McLachlan had obtained eggs from another ordinary female of the 

 same species, and they were brought to maturity for him by the Eev. 

 E. Horton ; but during the time these were feeding up and coming 

 to perfection the sun shone brilliantly almost every day. These two 

 lots did not differ two days from the time of the eggs being deposited 

 to the time of the appearance of the first imago, yet Mr. Bond's were 

 very dark, dull specimens, without the slightest tint of rosy, and Mr. 

 McLachlan's, with a single exception, were very bright with more 

 than an average of rose tint. Of course I do not say that in the one 

 case the dull weather produced the dull specimens, or that in the 

 other the bright sunshine produced the bright colours ; but the two 

 cases are very suggestive, and harmonise very well with my ideas of 

 light, heat, and colour. 



That light has some influence on the colours of lepidoptera I think 

 there can be little doubt. Mr. Sidebothom {Sc. Gos., Dec, 1869) 

 procured a large number of V. urticcB when quite small and fed them 

 up in three lots, one under blue light, one under yellow, and one 

 under ordinary light. " These reared in the blue light differed from 



