G. T, PORRITT : PRESIDENTIAL ADDRESS. 99 



I am g-iving- my illustrations almost entirely from my 

 experience among- lepidopterists, because I know most about 

 them ; but I doubt not the geologists, botanists, ornithologists 

 and others will bear me out in saying that the study of their 

 branches was carried out in pretty much the same way, and 

 that similar advances, though sometimes in different directions, 

 have been slowly but surely made. 



Labelling soon led the way to a further advance — larger 

 series of each species. Labelling often shewed that specimens 

 of a species received from a certain area, perhaps of consider- 

 able extent, or sometimes of only a mile or two square, say in 

 West Yorkshire or Scotland, varied very little among them- 

 selves, but when placed alongside the specimens of the same 

 species from areas in the South of England, were altogether 

 different from them, whilst both forms might again be widely 

 different from the same species from localities in Wales or 

 Ireland, and so on. It became apparent at once that our 

 cabinets must be re-arranged, and instead of leaving space for 

 two or four specimens, the orthodox way with our entomological 

 fathers, we must have room enough for at least ten or a dozen, 

 and in the case of many species for even 70 or 80 or more, in 

 order to adequately represent and study their local and racial 

 variations. Possibly the extraordinary interest aroused by 

 and through the study of this local variation in lepidoptera has 

 had more to do with the immense advance made in lepidoptero- 

 logical science during the past 20 years or more than anything- 

 else. To find out the causes one had to become interested in the 

 geology, the botany, the dryness or the moistness of the 

 climate, the amount of sun, and a score of other things affect- 

 ing the different areas, including the amount of smoke or soot, 

 which in the south West Riding- districts of our county, has, by 

 some been considered responsible, in the struggle for existence 

 (for indirectly of course, through these various agencies, it must 

 be the survival of the fittest which has created the variation), 

 for the many extreme melanic forms, some of them clearly of 

 comparatively recent formation, for which especially the south 

 West Riding district has become so notorious. This is not the 

 time to enter into a discussion on variation and melanism ; 

 suffice it to say that the study of it at once opened oat interest 

 in numberless other complex problems ; such as the origin of 

 the bands, spots, etc., so constant in entire groups of otherwise 

 dissimilar species ; how these bands and spots have become 

 altogether eliminated in other groups having clearly a common 

 ancestral origin with the banded forms, etc. Other students 

 became fascinated witn the study of the antennse ; studied the 

 scent glands ; the folds of the wing-membranes ; the venation ; 

 and a hundred other thing-s in connection with the perfect 

 insect. Then the study of the earlier stages, — the eggs, the 

 larvse, the pupae, all have their votaries, though the first and 

 last have perhaps not so much engaged the attention of our 



