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JOURNAL OF VARIATION. 



No. 12. Vol. I. March 16th, 1891. 



MELANISM AND MELANOCHROISM IN BRITISH 

 LEPIDOPTERA. 



By J. W. TUTT, F.E.S. 

 {Continued front page 300.) 

 SEASONALLY dimorphic species on which I have 

 frequently experimented is Tephrosia crepuscularia 

 {Jancinria). The March and April broods, from 

 eggs laid in April, larvae feeding throughout April, 

 May, June, July, and very frequently August,^ produce moths 

 generally of a deep ochreous tint, varying somewhat in 

 intensity according to the woods in which they are found 

 (due probably to "natural selection") but still always more 

 or less ochreous. The second brood, from eggs laid in 

 April, larvae feeding in May and June, produce pale whitish 

 moths (no ochreous colour) in July.^ I have repeatedly had a 

 large brood, eggs all laid at one time, hatch simultaneously, — 

 part of the larvae feed up, pupate and emerge in eight or nine 

 weeks producing the pale form, — whilst the remainder of the 

 brood (under the same conditions) have fed slowly on, pupated 

 in some fifteen or sixteen weeks, lain over as pupae until March, 

 and then produced the ochreous form, I have forced these 

 autumnal pupae, so as to obtain emergence throughout 

 January, but they never produced anything except the ochreous 

 (spring) brood. Now if Mr. Merrifield's conclusions previously 

 referred to, were at all capable of generalisation, these forced 

 specimens ought to be pale, but they never are, and I would 

 suggest that the cause of difference is in the retarded larval 

 conditions and the influence of heredity which makes one part 

 of the brood grow, slowly and pass the winter as pupae before 



' I think T. crepuscularia is one of the slowest feeding species I ever reared. 

 - The larvps from this emergence are just as slow in feeding up, and are rarely 

 full-fed before October. 



