MELANISM AND MELANOCHROISM. 321 



T<2niocampa, etc., of all of which species I possess banded 

 specimens, — all these I look upon as cases of progressive develop- 

 ment towards a banded form, brought about or strongly aided by 

 " natural selection " — rather than cases of heredity, disease, or 

 reversion. Dark vars. of Fidonia atomaria and Strenia clathrata 

 I look upon more in the light of true melanisms. 



I have given several cases of " progressive development " 

 tending to produce more or less partial melanism, but I am 

 quite aware that it is possible to follow out these cases in the 

 opposite direction to that which I have done, and look on 

 them as cases of reversion. To me, no family of moths shows 

 such ample proof of a tendency to become melanic by rever- 

 sion as our so-called "Carpet " moths, comprising the Geome- 

 trid genera — Melanthia, Meianippe, Coreniia, Cainptograuuiia, 

 and the allied Larentia and Emmelesia. I consider the most 

 highly developed forms of these genera to be those specimens 

 which are practically unicolorous, white, buff, or golden, with 

 an entire (or almost entire) absence of transverse bands. I 

 look on the least specialised forms as those which are dark in 

 colour, covered with dark transverse wavy lines, with but rare 

 tendency to banded form. I will take a few specimens as 

 types of the whole group. Meianippe hastata var. liastulata (?), 

 found in Scotland and the Hebrides, has the broad black 

 transverse bands broken up into narrower bands and liner 

 transverse lines. MelantJiia rubiginata, the type in the 

 southern districts of Britain, has only faint traces of dark central 

 and marginal bands : as we get further west and north, the 

 complete central-banded form (var. virgatd) becomes typical ; 

 in certain parts of Ireland and Scotland no other form appears 

 to be known; in theTrossachs and other West Scotland districts, 

 the banded form is partly replaced by an unicolorous blackish 

 form iyzx. plumbatd) with transverse lines. Mclantlna albicil- 

 lata occasionally throws a form (var. sitffiisd) parallel to rubi- 

 ginata var. plwnbata. Meianippe tristata varies locally, in some 

 districts the whole area of the wing is covered with transverse 

 lines, in others the central area is very distinctly banded. M. 

 sociata, a distinctly banded species on a white ground, in the 

 south, exists in the Hebrides as a species with the transverse 

 lines on a dark ground. M. montanata, occasionally almost 

 pure white, frequently has the central band only represented 

 by two darker external transverse lines, becomes more com- 

 pletely banded normally as we go north and west, until, in the 

 Shetlands, the ground colour becomes greyish ochreous and the 



