J. W. H. Harrison 257 



filigrammaria and (2) is of an ochreous grey tone entirely different 

 from the monotonous quaker grey ofautumnota or the violently chequered 

 mass of filigrammaria where the powerful banding (of the deepest 

 chocolate or carob brown obtainable) almost overpowers the dark fuscous 

 shading of the ground and its pure white wedge-like interruptions. The 

 significance of this will be grasped at once when attention is drawn to 

 the fact that colour differences in these insects are not qualitative but 

 are correlated with the quantity of pigment present. In filigrammaria 

 the brown pigment is in excess ; therefore it appears a photographic 

 black ; in autumnata it is slight and mixed with silvery white and hence 

 looks grey ; whilst in the hybrid it is medium so we get the impression 

 of ochreous. 



But, as with their cousins, a considerable range of fluctuating varia- 

 tion is observable in the vigour of the banding. Some, in the two 

 central bands, are quite as clearly marked as fi^iigrammaria, but this is 

 counteracted by a lack of vigour in the presubterminal bar which com- 

 bines the obsolescence of the corresponding avtumnata band and the 

 strength of that of filigrammaria. This, in combination with the lack 

 of silkiness in tone, will 'always prevent one's confusing these insects 

 with pure filigrammaria, in spite of their possessing the white wedges 

 regularly outlining the cell in filigrammaria and occasionally perceptible 

 on the nervures. Corroborative evidence too can be gleaned from the 

 hindwings ; on these filigrammaria possesses a well marked presub- 

 terminal band ; autumnata displays a feeble one with a stronger terminal 

 suffusion ; the hybrid compromises. 



From these heavily banded types we pass by degrees to insects 

 exhibiting the whole range of variation in autumnata grey ground, in 

 union with every degree of depth in ihe filigrammaria ty^^e of banding, 

 so that in the end we reach, especially in the male, insects appearing at 

 first sight indistinguishable from pure autumnata except in size. For 

 the most part these betray their mixed blood not only in size but, on 

 careful examination, in the exaggerated strength of the presubterminal 

 band when compared with autumnata ; if they do not, and the cases are 

 few, the clear white wedges of filigrammaria serve to indicate their 

 hybrid origin. But, whilst in all cases at least one of these points 

 serves to direct one's judgment, in many of the most autumnata-\\ke 

 individuals both features appear to help one. 



In connection with the relative size of the sexes the F^ insect like- 

 wise seems intermediate. In filigrammaria the female size is 88*7 °/^ 

 of that of the male, in autumnata it is 907 "/^ and in the F^ insects 898 °l^. 



