Seasonal Dimooyhism in Butter flies. 103 



Brisbane, given above ; while the fact recorded by Dr. 

 Martin {loc. cit.) that among many hundreds of both sexes 

 of C. crocale, all presumably belonging to one emergence, 

 taken by him near Bindjei, there was not a single C. 

 catilla (pomona), may possibly have a similar significance.* 



It is not a little remarkable that although there are 

 forty-three specimens of C. immona, and G. crocale in the 

 Hope collection duly labelled with locality and date, they 

 cannot be said to throw much light on the question of 

 seasonal dimorphism. What is wanted is a long series of 

 observations carefully carried on in one locality, and 

 accompanied, if possible, by breeding experiments. 



If, as is probable, it should eventually be shown beyond 

 doubt that the different forms of G. pomona, though 

 related to the seasons in some part of its range, occur 

 indifferently at all times in others, the case would by no 

 means stand alone. I propose in the next place to notice 

 very briefly several statements that have been made by 

 different authorities with regard to other species, which 

 statements tend to show that in many cases where the 

 existence of seasonal modification has been reasonably 

 presumed, or even actually demonstrated, the seasonal 

 relation is far from being rigidly fixed in all parts of the 

 area of distribution. 



2. Seasonal Dimorphism in Catopsilia pyrantlic, Linn. 



The first instance that may be taken is that of Catopsilia 

 p)yrantlic, Linn. This butterfly grades imperceptibly into 

 C. gnoma, Fabr. just as G. crocale does into G. pomona. 

 Here again, in the absence of breeding experiments, the 

 absolute proof of specific identity is still lacking ; but de 

 Niceville had no doubt, from his own observations, that the 

 two forms represent a single species. In this case he is 

 able to assign a seasonal value to the two forms, — C. 

 pyranthc being in his opinion the wet-season, and C. gnoma 

 the dry-season phase of the species. But the point of 

 special interest, in view of the irregularity that appears to 

 obtain in the seasonal relations of G. crocale and C. pomona, 



* It should, however, be noted that "N.-E. Sumatra does not 

 possess a well-marked dry and wet season, such as is found over 

 most of the continent of India, there being no month in the year 

 when it does not rain." Journ. Asiat. Soc. Bengal, LXIV, 1895, 

 pt. ii, p. 362. See below, jx 196. 



