ON THE VAEIATION OP INSECTS. 55 



Coenonympha davus, dark form in Shetland Isles, Newman Brit. 

 Butt. 97. Colias edusa sufusa, Ent. xi., Newman Brit. Butt. 

 144. C. philodice suffusa, Massachusetts, Maynard, Butt, of 

 New Eng., pi. vii., fig. 57c. Pieris hrassicce nigrescens, Newman 

 Brit. Butt. 165, Cirrlioedia xerampelina ohscura, Entoin. xvi. 

 236. Eubolia plumharia nigrescens, ^ntom.x\\. 138. Melanthia 

 albicillata suffusa, Carrington. Hyhernia defoliaria siffusa, Ckll. 

 Chelonia caia ohscura, Newman, Brit, Moths, 33; Entom.xi. 103. 

 Abraxas grossulariata ohscura, Newman, Brit. Moths, 100. See 

 also Entom. 1887, 216, for a grey variety. Melanippe hastata 

 nigrescens, tom. cit. p. 157. Acronycta rumicis ohscura, id. p. 

 255 ; and A. menyanthidis salicis. Curt. Xylophasia monoglypha 

 ■nigrescens, id. p. 285. Satyrus alope maritima, Edw., a small 

 and dark maritime form (Long I. &c.. United States). Larentia 

 olivata semisuffusa, Proc. S. Lond. Ent. Soc. 1886, 53, pi. 1, fig. 

 1. Amphidasys hetularia douhledayaria. Mill. Diurnea fagella, 

 melanic varieties now prevalent at Huddersfield, Ent. Mo. Mag, 

 1887, 140. Anoplodera sexguttata niger, Entom. x. 214. Ptero- 

 stichus cupreus niger, Entom. xii. 110 (T. H. Hart). Lema 

 melanopa nigra, and L. cyanella nigrescens, loc. cit. Sphecodes 

 gihbus niger, ^ , and S. ephippium niger, 3' , near Hastings, 

 Entom. xi. 17. — Melanism is a subject that comes up periodically 

 and causes considerable discussion, but is nevertheless ver}' far 

 from being settled. I have expressed the opinion in a former 

 paper that dampness in the atmosphere — clouds, mists, and so 

 on — has a great deal to do with its production, yet I confess that 

 it is probable that other factors are also at work. I have given a 

 good long list above, but it really represents only a very small 

 fraction of the known forms of this kind, and I have tried to 

 make it as representative as possible. In connection with 

 this list the following facts will be noticed : — 



1. The small number of American examples : it appears 

 certain that melanism as usually seen in Europe is rare in North 

 America, a circumstance that is strongly against the theory of its 

 being caused by cold. " A straw will show which way the wind 

 blows," so it is interesting that, according to Mr. R. H. Meade, one 

 of the chief points of difference between American and European 

 species of Sarcophaga, is that in the former the anal segments are 

 generally red or yellow, while in the latter they are black or grey. 

 The species of this genus I have taken in Colorado have the anal 

 segments red or reddish, confirming this statement. 



2. The alpine forms : dark mountain varieties are well known 

 throughout Europe. Mr. A. H, Swinton (Ent. Mo. Mag. 1885, 

 231) remarks on the melanic tendency exhibited by Asturian 

 mountain insects, particularly the Orthoptera. Here in Colorado 

 the species of Colias found high upon the mountains (10,000 ft. 

 upwards) is of so much darker a yellow than the species occurring 



