On the genesis of the species / by St. George Mivart.

Date:
1871
Catalogue details

Licence: Public Domain Mark

Credit: On the genesis of the species / by St. George Mivart. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    variations as to the length of the neck have been accompanied by some unfavourable variation in some other part, neutralizing the action of the favourable one, the latter, moreover, only taking effect during these periods of drought! How often must not individuals, favoured by a slightly increased length of neck, have failed to enjoy the elevated foliage which they had not strength or endurance to attain ; while other individuals, excep- tionally robust, could struggle on yet further till they arrived at vegetation within their reach. However, allowing this example to pass, many other instances will be found to present great difficulties. Let us take the cases of mimicry amongst lepidoptera and other insects. Of this subject Mr. Wallace has given ai most interesting and complete account,^ showing in how many and strange instances this superficial resemblance by one creature to some other quite distinct creature acts as a safeguard to the first. One or two instances must here suffice. In South America there is a family of butterflies, termed Heliconidoe, which are very conspi- cuously coloured and slow in flight, and yet the individuals abound in prodigious numbers, and take no precautions to conceal them- selves, even when at rest, during the night. Mr. Bates (the author of the very interesting work The' Naturalist on the Eiver Amazons, and the discoverer of Mimicry) found that these conspicuous butterflies had a very strong and disagreeable odour; so much so that any one handling them and squeezing them, as a collector must do, has his fingers stained and so infected by the smell, as to require time and much trouble to remove it. It is suggested that this unpleasant quality is the cause of the abundance of the Heliconidse; Mr. Bates and other observers reporting that they have never seen them attacked by the birds, reptiles, or insects which prey upon other lepidoptera. Kow it is a curious fact that very different South American ^ See Natural Selection, chap. iii. p. 45.
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