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different genera ; and the former is a native of Mexico, while the one now described comes from Adelaide in Australia. The two species, therefore, cannot be descended one from the other; and the conclusion seems inevitable that the modification has originated independently in the two species.
It is interesting that, although these specimens apparently never leave the nest, and have little use therefore for legs, mandibles, &c., the modifications which they have undergone seem almost confined to the abdominal portion of the digestive organs. The head and thorax, antennæ, jaws, legs, &c. differ but little from those of ordinary ants.
ON THE RELATION OF ANTS TO PLANTS.
It is now generally admitted that the form and colour, the scent and honey of flowers, are mainly due to the unconscious agency of insects, and especially of bees. Ants have not exercised so great an influence over the vegetable kingdom, nevertheless they have by no means been without effect.
The great object of the beauty, scent, and honey of flowers, is to secure cross fertilisation; but for this purpose winged insects are almost necessary, because they fly readily from one plant to another, and generally confine themselves for a certain time to the same species. Creeping insects, on the other hand, naturally would pass from one flower to another on the same plant; and as Mr. Darwin has shown, it is desirable that the pollen should be brought from a different plant altogether. Moreover, when ants quit a plant, they naturally creep up another close by, without any regard to species. Hence, even to small flowers, such as many crucifers, composites, saxifrages, &c., which, as far as size is concerned, might well be fertilised by ants, the visits of flying insects are much more advantageous. Moreover, if larger flowers were visited by ants, not only would they deprive the flowers of their honey without fulfilling any useful function in return, but they would probably prevent the really useful visits of bees. If you touch an ant with a needle or a bristle, she is almost sure to seize it in her jaws; and if bees, when visiting any particular plant, were liable to have the delicate tip of their proboscis seized on by the horny jaws of an ant, we may be sure that such a species of plant would soon cease to be visited. On the other hand, we know how fond ants are of honey, and how zealously and unremittingly they search for food. How is it then that they do not anticipate the bees, and secure the honey for themselves ? This is guarded against in several ways.
Belt appears to have been the first naturalist to call attention to this interesting subject.
Many flowers,' he says, “have contrivances for preventing useless insects from obtaining access to the nectaries.
• Great attention has of late years been paid by naturalists to the wonderful contrivances amongst flowers to secure cross fertilisation, but the structure of many cannot, I believe, be understood, unless we take into consideration not only the beautiful adaptations for securing the services of the proper insect or bird, but also the contrivances for preventing insects that would not be useful from obtaining access to the nectar. Thus the immense length of the Angroecum sesquipedale of Madagascar might, perhaps, have been more easily explained by Mr. Wallace, if this important purpose
1 The Naturalist in Nicaragua. By Tbos. Belt, F.G.S., pp. 131 and 133.
had been taken into account.' Kerner has since published a very interesting work,' especially devoted to the subject, which has been translated into English by Dr. Ogle.
In aquatic plants, of course, the access of ants is precluded by the isolation in water. Nay, even many land plants have secured to themselves the same advantage, the leaves forming a cup round the stem. Some species have such a leaf-cup at each joint, in others there is only a single basin, formed by the rosette of radical leaves. In these receptacles rain and dew not only collect, but are retained for a considerable time. In our own country Dipsacus sylvestris (the common teazle) is the best marked instance of this mode of protection, though it is possible that these cups serve another purpose, and form, as suggested by Francis Darwin, traps in which insects are caught, and in which they are dissolved by the contained fluid, so as to serve as food for the plant. However this may be, the basins are generally found to contain water, even if no rain has fallen for some days, and must, therefore, serve to prevent the access of ants.
The next mode of protection is by means of slippery
! Kerner: Flowers and their Unbidden Guests.
surfaces. In this case, also, the leaves often form a collar round the stem, with curved surfaces over which ants cannot climb. "I have assured myself,' says Kerner, 'not only by observation, but by experiment, that wingless insects, and notably ants, find it impossible to mount upwards over such leaves as these. The little creatures run up the stem, and may even not unfrequently traverse the under surface of the leaves, if not too smooth ; but the reflexed and slippery margin is more than the best climbers among them can get over, and if they attempt it they invariably fall to the ground. There is no necessity for the lamina of the leaf to be very broad ; even narrow leaves, as, for instance, those of Gentiana verna, are enough for the purpose, supposing, of course, that the margin is bent backwards in the way described.'
Of this mode of protection the cyclamen and snowdrop offer familiar examples. In vain do ants attempt to obtain access to such flowers, the curved surfaces baffle them; when they come to the edge they inevitably drop off to the ground again. In fact, these pendulous flowers protect the honey as effectually from the access of ants, as the hanging nests of the weaver and other birds protect their eggs and young from the attacks of reptiles.
Iu a third series of plants the access of creeping insects is impeded or altogether prevented by certain parts of the flower being crowded together so as to leave either a very narrow passage or none at all. Thus