1907.] 71 



The outgoing President, VIr. F. Merrifield, tlieii delivered his address, in which 

 lie discussed some of the causes of the persistent abundance or scarcity, generally 

 or locally, of species and varieties of insects, and the relative imjiortance of the 

 consumption of their food, and the attacks of their enemies. Reference was made 

 to striking characters, that seemed of no biological importance, to habits and 

 activities not directly concerned with nutrition or reproduction, and the manner in 

 whicii they are affected by externa] conditions ; and to structure and fixed habits 

 indicating tiieir ancestral history and affecting their present capabilities. — 

 H. Rowland-Brown, Hon. Secretary. 



PROaRESSIVE MELANISM : 



FURTHER NOTES ON HASTULA STERANA, Mill. 



BY T. A. CHAPMAN, M.D., F.Z.S. 



{^Continued from page 35). 



Plate II. 



]f we assume that Melanism is provided by Les Maurettes and 

 resented by La Plage, and that the difficulty of intercrossing between 

 the two localities is considerable, it seems that the proportions of 

 melauic specimens in the two places is hardly so different as one 

 would expect. It is probable, therefore, that the hyerana form is 

 still not much less adapted to the Maurettes than marginata. As 

 regards La Plage it must be remembered that the Costebelle locality 

 is fairly extensive, and is nearly, if not quite, continuous with the La 

 Plage locality, yet its conditions are very nearly the same as those of 

 the Maurettes, and differ from those of La Plage proper in much the 

 same way as do the Maurettes themselves ; therefore, as regards the 

 question of La Plage getting rid of the melanic marginata, the exis- 

 tence of a powerful traitor in the camp must be taken into account. 



A census of moths at Costebelle would be veiy useful in further 

 elucidating this, but it is not available. 



Whether the different tendency as regards producing melanism 

 in R. hyerana, between La Plage and the Maurettes, be as great as I 

 suspect, or be merely moderate, it unquestionably exists. ^Some con- 

 dition is found in the Maurettes that is absent, or, at any rate, much 

 weaker at La Plage. 



To reach this conclusion is a distinct advance in our knowledge. 

 At present, I think, we can go very little further, but it may be well 

 to survey the ground in front and make some sort of working 

 hypothesis, if possible. 



