specific modifications of Japan Carabi. 519 



theory, the sooner we shall discard it, for a better know- 

 ledge of the cause of colour in living organisms will 

 dissipate it. 



Nature has no multiform manner of working ; her 

 energy would be weakened unless based on uniformity 

 of action, but she obtains many ends by the most simple 

 means, and as solar-rays appear to produce metallic 

 colours in insects, so air and its components seem to 

 produce scales and feathers. Nosoderma has a weather- 

 beaten cuticle, and so has Anthrihus and other beetles, 

 which stick to trees in the daytime like Noctucs. The 

 under side of a butterfly is weather-beaten, while we 

 have seen the upper side is protected from nocturnal 

 vapours and bad weather. What happens to the butter- 

 fly beneath happens to the moth and beetle above — its 

 surface is weather-beaten. It is the under surface of 

 the moth which would become brilliant if exposed to the 

 sun. In many Lepidoptera the upper margin of the 

 secondary wing, near the base, is covered- by the lower 

 margin of the primary wing. The upper surface of this 

 part, the costal margin, has neither colour nor scales. 

 If there were no scales on the under side it would be 

 transparent. This small space is neither sun-struck nor 

 weather-beaten. Attrition is absent. We have said that 

 where direct solar-rays can act permanently on feathers 

 and scales, colour must come ; and where air touches 

 the cuticle of animals, there are scales, feathers, and 

 hair. There are no scales or plumes on the wings of 

 insects when the surface is protected from the air, nor is 

 there bright colour in a surface not touched directly by 

 the solar-ray. The under wing of a Dytiscus, or a 

 Lucanus, is kept from air and light, and it is transparent, 

 that is, it is neither coloured nor scaled. Air, apparently, 

 so universally gives hair and feathers to animals that 

 we think that it is necessary tp the welfare of the 

 creatures so to be covered ; and it is so, since they have 

 been modified to their present form. But, if air has 

 caused scales and feathers, it is only by acting on a 

 physiological structure prepared by previous modification 

 to be again modified by its power, after the manner here 

 indicated regarding light. For as colour will come on a 

 structure suitable to retain it, whether it be the elytra of 

 a beetle or the lamelliform feather of a bird, so hair will 

 come on animals and feathers on birds through the 

 action of the air, although they may be of no original 



TRANS. ENT. SOC. 1882. PART IV. (DEC.) 3 Y 



