The British Noctuæ and Their Varieties, Vol. 2 (Classic Reprint)
| Preis: | 18.95 EUR* (inkl. MWST zzgl. Versand - Preis kann jetzt höher sein!) |
| Versand: | 0.00 EUR Versandkostenfrei innerhalb von Deutschland |
| Partner: | buecher.de |
| Hersteller: | Forgotten Books (Tutt, J. W.) |
| Stand: | 2015-08-04 03:50:33 |
Produktbeschreibung
Excerpt from The British Noctuæ and Their Varieties, Vol. 2 In the introduction to Vol. I of this work, I referred shortly to the extent and probable causes of variation in the Nootuæ, and do not now propose to travel further in the same direction, but rather to extend the view over a few particular points not then dealt with. There are, however, one or two suggestions previously mentioned which have received valuable confirmation during the last few months, and to these I will briefly refer. In the introduction to Vol. I., pp. xv-xvi., I referred cursorily to disease, as being a potent factor in producing variation, generally in a direction tending towards melanism. Mr. Merrifield, to whom we are greatly indebted for some valuable experiments relating to the influence of temperature on pupæ in producing colour variation in the resultant imagines, has made further experiments this year, one of the species operated on being Vanessa urticæ. I was fortunate in being present at the meeting of the London Entomological Society when these specimens were exhibited, and my idea that the darkening produced in Mr. Merrifield´s experiments was due to some form of disease received the fullest confirmation. The specimens exhibited did, certainly, display a fair amount of variation, and those which had been exposed artificially to the greatest and most continued cold were the darkest, but, at the same time, with scarcely a single exception, were all more or less deformed. The result of the application of artificial cold here becomes self-evident. The suspense of the vital functions, at a time just previous to emergence, when they should be most active, undoubtedly affects injuriously the constitution of the pupæ, the resulting imagines, if any, being deformed, ill-developed as to scale structure, and may become rather paler, or darker according as the retrogression naturally tends towards a paler or darker coloration. The influence of excessive artificial cold, in producing variation is now comparatively clear. It appears to be entirely indirect, and simply acts by producing a diseased condition in the pupa, and a resultant imago more or less deformed. It also appears to prevent the proper formation of pigment and hence produces, as it were, an excess of non-pigmental scales at the expense of the normal ones. The general obsolescence of characteristic colour and markings, in those species which are essentially Arctic, is now explained, as we see that the vital functions are less active and therefore not so capable of developing scale and pigment. In some butterflies, the resulting influence differs from that in some moths, as the influence of "natural selection" is generally so essentially diverse in the two groups; and the result of retrogression is also different. As an illustration of what I mean, it may be safely assumed, that the red-brown of polychloros and the bright red of urticæ are both equally developed through yellow. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.
* Preis kann jetzt höher sein. Den aktuellen Stand und Informationen zu den Versandkosten finden sie auf der Homepage unseres Partners.
Folgende Produkte könnten dir ebenso gefallen
