For further instances of the power of smell in snails, see chap. [vii].
Slugs have been known to make their way into bee-hives, presumably for the sake of the honey.[73] ‘Sugaring’ the trees at night for moths will often attract a surprising concourse of slugs. Sometimes a particular plant in a greenhouse will become the object of the slugs’ persistent attacks, and they will neglect every other food in order to obtain it. Farfugium grande is one of these favourite foods, “the young leaves and shoots being always eaten in preference to all other plants growing in the houses; where no Farfugiums were kept the slugs nibbled indiscriminately at many kinds.”[74] The flowers of orchidaceous plants exercise a special attraction over slugs, which appear to have some means of discovering when the plants are in bloom. “I have often observed,” says Mr. T. Baines, “that a slug will travel over the surface of a pot in which is growing a Dendrobium nobile, a Cattleya, Vanda, or similar upright plant for a score of times without ever attempting to ascend into the head of the plant unless it is in bloom, in which case they are certain to find their way straight to the flowers; after which they will descend, and return to some favourite hiding-place, often at the opposite end of the house.”[75] Mr. R. Warner has “actually seen many little slugs suspending themselves by slime-threads from the rafters and descending on the spikes of the beautiful Odontoglossum alexandrae; and thus many spikes, thickly wadded round with cotton wool (which the slugs could not travel over), and growing in pots surrounded by water, had been lost.”[76] Perhaps the most singular instance of a liking for a particular food is that related by Mr. E. Step.[77] In a London publishing house, slugs were observed, during a period of nearly twelve months, to have fed almost nightly on the colouring matter in certain bookcovers, and though the trails were often seen over the shelves, and cabbage and lettuce leaves laid down to tempt the creatures, they continued their depredations with impunity for the time above mentioned.
Limnaea peregra has been observed feeding on old fish-heads thrown into a dirty stream, and a large gathering of Limnaea stagnalis has been noticed feeding upon an old newspaper in a pond on Chislehurst Common, ‘so that for the space of about a square foot nothing else could be seen.’[78]
Tenacity of Life.—Land Mollusca have been known to exhibit, under unusual conditions, remarkable tenacity of life. Some of the most noteworthy and best authenticated instances of this faculty may be here mentioned.
The well-known story of the British Museum snail is thus related by Mr. Baird.[79] On the 25th March 1846 two specimens of Helix desertorum, collected by Charles Lamb, Esq., in Egypt some time previously, were fixed upon tablets and placed in the collection among the other Mollusca of the Museum. There they remained fast gummed to the tablet. About the 15th March 1850, having occasion to examine some shells in the same case, Mr. Baird noticed a recently formed epiphragm over the mouth of one of these snails. On removing the snails from the tablet and placing them in tepid water, one of them came out of its shell, and the next day ate some cabbage leaf. A month or two afterwards it began repairing the lip of its shell, which was broken when it was first affixed to the tablet.
While resident in Porto Santo, from 27th April to 4th May 1848, Mr. S. P. Woodward[80] collected a number of Helices and sorted them out into separate pill-boxes. On returning home, these boxes were placed in empty drawers in an insect cabinet, and on 19th October 1850, nearly two and a half years afterwards, many of them were found to be still alive. A whole bagful of H. turricula, collected on the Ilheo de Cima on 24th April 1849, were all alive at the above-mentioned date.
In September 1858 Mr. Bryce Wright sent[81] to the British Museum two specimens of H. desertorum which had been dormant for four years. They were originally collected in Egypt by a Mr. Vernèdi, who, in May 1854, while stopping at one of the stations in the desert, found a heap of thorn-bushes lying in a corner of the building, rather thickly studded with the snails. He picked off fifteen or twenty specimens, which he carried home and locked up in a drawer, where they remained undisturbed until he gave two to Mr. Wright in September 1858.
In June 1855 Dr. Woodward placed specimens of H. candidissima and H. aperta in a glass box, to test their tenacity of life; he writes of their being still alive in April 1859.
Mr. R. E. C. Stearns records[82] a case of Buliminus pallidior and H. Veatchii from Cerros I. living without food from 1859 to March 1865.
H. Aucapitaine mentions[83] a case of H. lactea found in calcinated ground in a part of the Sahara heated to 122° F., where no rain was said to have fallen for five years. The specimen revived after being enclosed in a bottle for three and a half years.