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Show 1889.] MR. A. G BUTLER ON A NEW FOSSIL MOTH. 293 In the list of Insect-remains determined by the late Mr. Frederick Smith of the Zoological Department, two Lepidopterous insects, referred to a species of Lithosia, are recorded. The fossil now to be described is especially interesting on account of its unusually perfect condition, which not only enables one to trace without difficulty the main features of its structure, but gives a very good idea of its pattern and colouring when living. A study both of fossil and recent Lepidoptera leads one to the conclusion that the Butterflies and Moths of the past were by no means so highly coloured as those of th*3 present day ; that in the earlier ages of tbe world the large family Nymphalidae was represented by brown and black species, the Pierinae bv species wholly white, or white bordered with black ; the Hesperiidee and most, if* not all, of the Moths by brown, black, and white forms. Even at the present day these three types of colouring are far in excess of more brilliant hues, and the fact of dull coloration being, as a rule, more abundantly found in female than male Lepidoptera, even in the more brightly coloured genera, tends to prove that sexual selection has been the principal agent in beautifying the species now existing. The Lepidopteron found by Mr. A'Court Smith belongs to the Euschemidae, a family of Geometrid Moths allied to tbe Zerenidae (popularly called Magpie moths) and containing some of the most brilliantly coloured of all known Heterocerous Lepidoptera; it, however, does not belong to the brilliant section of the family, but to a small group of genera for the most part black and white to the present day, though some of them have acquired yellow markings. Assuming that the Euschemidae originally consisted of black and white insects, yellow would naturally be the first departure, on account of its being contained in the largest proportion in whitel ; and it would follow that in this family yellow markings would be most likely to preponderate at the present time, as, in fact, they do, whilst the black portions of the wing when modified show a violet or, in the more highly specialized forms, a bright blue shot tint. Mr. A'Court Smith's discovery belongs to a group of three or four genera which to this day retain their original neutral tints of black and white, and which therefore are in all probability the oldest existing representatives of the family Euschemidae ; these genera are Calospila, Simena, Mniocera, and Craspedosis ; other genera pro-bablv remain to be discovered. It is a significant fact, as evidencing the permanence of Lepidopterous forms, that, although at the present time we have numerous brilliantly coloured species and even genera, the primitive forms still have their representatives in nearly allied genera, the colours of which remain dull and the patterns but little modified. This is most easily seen in the best preserved and more recent fossils, such as Neorinopis represented by the black and white Neorina, Mylothrites by the brown forms of Precis, the so-called Pontia freyeri by the females of the S.-American P. suasa, and Thanaites by Thanaos; the affinities of 1 White light contains a proportion of about T 7 ff yellow. PROC. ZOOL. Soc-1889, No. XX. 20 |
