The Readable Darwin by Pechenik Jan A.;

Author:Pechenik, Jan A.;
Language: eng
Format: epub
Publisher: Oxford University Press, Incorporated
Published: 2022-03-15T00:00:00+00:00

Figure 8.6 Some driver ant workers (such as these Dorylus sp.) are much larger than other workers of the same species.

With these facts before me, I believe that natural selection, by acting on the fertile ants (the parents), could create a species that should regularly produce neuters, all of large size with one form of jaw, or all of small size with widely different jaws, or even—and this is the greatest difficulty—produce one set of workers of one size and structure and simultaneously another set of workers of a different size and structure: first a graduated series is formed in a colony, as in the case of the driver ant just described, and then the extreme forms are produced in greater and greater numbers, generation after generation, through the heightened survival of the fertile parents that generated them, until none is produced with an intermediate structure.20

An analogous explanation has been given by Mr. Alfred Russel Wallace21 of the equally complex case of certain Malayan butterflies regularly appearing under two or even three distinct female forms. Similarly, Fritz Müller has presented a similar explanation for certain Brazilian crustaceans that likewise appear in two very different male forms.

I have now explained how, I believe, the wonderful fact of two distinctly defined castes of sterile female workers existing in the same nest, both widely different from each other and from their parents, has originated. We can see how useful their production may have been to a community of social ants, on the same principle that a division of labor is useful in civilized human societies. Ants, however, work by inherited instincts and by inherited organs or tools, while we work through acquired knowledge and manufactured instruments. But I must confess that, even with all my faith in natural selection, I could never have appreciated that this principle could be efficient to such a high degree had not the case of these neuter insects led me to this conclusion. I have therefore discussed this case at some little but still insufficient length in order to show the power of natural selection, and likewise because this is by far the most serious special difficulty that my theory has encountered. The case is also very interesting as it proves that, with both animals and plants, any amount of modification may eventually be brought about by the gradual accumulation of numerous, small, spontaneous variations that are in any way beneficial, without exercise or habit having ever been brought into play: peculiar habits confined to the sterile workers, however long they might be followed, could not possibly affect anything about the males or the fertile females, which alone leave descendants.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.