specific modifications of Japan Carabi. 527 



affects form only. These two species run parallel to 

 Damaster hlaptoides and Lewisii, for both are nocturnal, 

 and present to us the first effect of thermal change, 

 i-iz., a structural modification, such as commonly occurs 

 in the flora- world when at the base of a mountain plants 

 show a vigorous growth and attain a large size, while 

 specimens higher up the mountain gradually diminish. 



Mr. Pryer has told us in a recent paper that certain 

 thermal or "temperature" forms of butterflies occur in 

 spring and others in summer, and that the forms are 

 regulated by the temperature in which the larvae live. 

 And this is not hard to understand. In Japan spring 

 forms of Lepidoptera come from larvae fed up on 

 autumnal foliage, on leaves, that is, which are fullj'' 

 matured, if not partially desiccated ; but the summer 

 broods are nourished on the succulent vegetation of 

 early summer. The nutritive properties in plants vary 

 as their growth is vigorous, or otherwise ; hence the 

 small mountain varieties of summer agree with those of 

 the spring in the valleys. Larvae reared on a patch of 

 poor soil in the midst of a fertile valley would give 

 a corresponding result. In the tropics the secret of the 

 "luxuriance lies in the copious rain," as I said, in 

 August, and the large size of' insects in the tropics is 

 owing to their association with, and dependence on, the 

 flora, and the conditions which affect both alike. A 

 collection of British beetles I can store in a cabinet of 

 fifteen drawers ; a collection containing the same number 

 of species from a country even as far north as Japan 

 occupies forty. 



I believe I have traced here in Carahiis the same lines 

 of variation which I noticed three years since in Da- 

 master, viz., that a robust or stunted form is an earlier 

 stage in thermal modification than colour, colour appear- 

 ing only as an insect requiring warmth becomes diurnal. 

 The discovery of the beautiful Carahus GeMnii in Hok- 

 kaido has introduced into the fauna of Japan an entirely 

 new phase of diurnal Carahus, and, although this species 

 at present stands apart from the other members of the 

 genus, we cannot fail t"o observe that its colours are sub- 

 dued, and by analogy we can anticipate the finding in 

 Saghalien of northern affinities which will be as bright 

 as the European auronitens* 



* Mr. Bates has just received this form in a fine new species from 

 lat. 46°. 



TRANS. ENT. SOC. 1882. — PART IV. (DEC.) 3 Z 



