33 



IV. The effects of artificial temperature on the colouring 

 of several species of Lepidoptera, ivith an account 

 of some experiments on the effects of light. By 

 Feeder! c Merrifield, F.E.S. 



[Read December 2na, 1891.] 



I HAVE on previous occasions proved that both the spring 

 and the summer emergence of Selenia illustraria, and the 

 one emergence of Ennomos autumnaria, are materially in- 

 fluenced in their colouring by exposure of the pupa in its 

 penultimate stage, — that is, in the one immediately pre- 

 ceding that in which the colouring of the perfect insect 

 begins to show, — to a moderate difference of temperature, 

 i. e., within the limits of 57' and 80" F., the lower causing 

 the greater darkness, and an exposure for a few days at 

 the higher temperature being sufficient for its purpose. 

 I have also proved that the markings of the former of 

 these species, and probably those of the latter, may be 

 very materially affected by long-continued exposure of 

 the pupa in its earlier stages to a much lower tempera- 

 ture, one of about 33°. 



Similar experiments have now been made on both 

 emergences of the other two English species of Selenia, 

 viz., S. illunaria and S. lunaria, with entirely similar 

 results as regards colouring. These results are least 

 marked in lunaria, as perhaps might have been expected 

 from the fact that that species is in England generally 

 single-brooded, and, where double-brooded, does not 

 manifest as much dimorphism as its congeners do. 



With respect to these Selenias, I now exhibit examples 

 taken from as many as fifteen separate "families" — a 

 term which I here use, not in its zoological sense, but as 

 a convenient one for describing the offspring of a single 

 pair. As the facts have now been established, and it 

 would be exceedingl}^ inconvenient and j^erhaps tiresome 

 to show the very long series that these fifteen separate 

 families have given me — more than 500 individuals — I 

 have on the present occasion limited myself, in the case 

 of the Selenias, to a selection of typical examples. But, 



TRANS. ENT. SOC. LOND. 1892,— PART I. (MARCH.) D 



