Volume IX FEBRUAKY, 1920 No. 3 



GENETICAL STUDIES IN THE MOTHS OF THE 

 GEOMETRID GENUS OPORABIA (OFORINIA) 

 WITH A SPECIAL CONSIDERATION OF MELAN- 

 . ISM IN THE LEPIDOPTERA. 



By J. W. HESLOP HARRISON, D.Sc. 



(With 13 Text-figures.) 

 CONTENTS. 



PAOE 



I. Introductory 195 



II. Variation — Subspecies — Local Kaoes — Melanism ...... 205 



(a) General 205 



(6) The evolution of the subspecies O. filigrammarla .... 209 



(c) The evolution of the local races . 214 



(d) The case of 0. dilutata and its subspecies 0. christyi . . . 228 



(e) The question of melanism ......... 229 



III. Breeding Experiments ......... . . 246 



(a) Inheritance of subspecific characters and of those characterising the 



local races 246 



(b) Inheritance within the Umits of the local races ..... 249 



(c) Inheritance of melanism ......... 249 



(d) Sex-linked inheritance ......... 250 



(e) Hybridisation experiments 254 



(1) Hybrids between 0. autumnata and O. filigrammaria . . 254 



(2) Hybrids between O. autumnata and O. dilutata . . . 266 



(3) Miscellaneous pairings •. 276 



IV. Summary 278 



I. Introductory. 



The genus Oporobia (now becoming known as OporiniaY is a homo- 

 geneous genus of the Geometridae, occurring throughout the Holarctic 

 region, but in spite of its enormous range possessing very few species, 

 in which peculiarity it resembles its nearest allies the genera Veniisia 

 and Cheimatohia. From the former the original phase of both Oporobia 



^ And in America as Epirrhita ! 

 Joarn. of Gen. ix 13 



