308 ENTOMOLOGICAL NEWS [July, '13 



I am not aware that intensifications so well marked in this 

 case can be produced by causes which may have given rise to 

 the pale forms previously described. 



Phigalia olivacearia Morr. f. nov. mephistaria (Figs. 8 and 9). 



Wings, thorax and abdomen blackish, smoky. Antennae normally 

 colored. Fringes of inner margin of secondaries whitish, otherwise 

 like the wing surface. Beneath the wings are a shade lighter than 

 above. Only a few faint traces of normal marking of wings, but veins 

 darker than ground color of wings. 



One male from West Roxbury, Mass., April 7, 1912; taken 

 by Mr. Walter F. Eastman in the day time from an electric 

 light post. 



Type in Mr. Eastman's collection. 



Among the North American Geometridae melanistic forms 

 are almost unknown. There are, however, large numbers of 

 such forms in the palaearctic fauna, and from year to year 

 new melanistic forms of Geometridae continue to be discov- 

 ered. Fifty years ago only one melanistic Geometrid was 

 known, the black doubled ayaria of Amphidasis betularius, and 

 this form at that time from England only. Now we find 

 doubledayaria and many other melanistic forms of palaearctic 

 Geometridae distributed over an increasingly larger area of 

 central Europe. Considered from a phylogenetical stand- 

 point, this yearly increase of melanistic forms is of the great- 

 est interest, and exact observations in localities, where such 

 forms appear and the publication of all details of capture is 

 very important. Up to date we are entirely incapable of stating 

 any rule as to the origin of melanistic forms in the field and 

 its increasing occurrence, although a number of theories have 

 been suggested as to its cause, but none of them as yet has 

 been sufficiently supported. We only know that melanistic 

 forms are certainly neither pathological nor degenerative 

 products (as many albinic forms are), for melanistic forms 

 are as a rule more strongly built and more resistant towards 

 climatic influences, etc., than their non-melanistic ancestors. 



We know two kinds of black coloration: nigrism, which 

 originates when the black (dark) markings of a wing become 

 more or less enlarged, and melanism, which signifies an in- 



