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noticed them first in Northern Brazil, in the province of Maranham; and afterwards at Pará. Every pouch was occupied by a nest of small black ants; and if the leaf was shaken ever so little, they would rush out and scour all over it in search of the aggressor. I must have tested some hundreds of leaves, and never shook one without the ants coming out, excepting one sickly-looking plant at Pará. In many of the pouches I noticed the eggs and young ants, and in some I saw a few dark-coloured coccidæ or aphides ; but my attention had not been at that time directed to the latter as supplying the ants with food, and I did not examine a sufficient number of pouches to determine whether they were constant occupants of the nests or not; but my experience since with the cecropia trees would lead me to expect that they were. If so, we have an instance of two insects and a plant living together, and all benefited by the companionship. The leaves of the plant are guarded by the ants; the ants are provided with houses by the plant, and food by the coccidæ or aphides; and the latter are effectually protected by the ants in their common habitation.
Amongst the numerous plants that do not provide houses, but attract ants to their leaves and flower-buds by means of glands secreting a honey-like liquid, are many epiphytal orchids, and I think all the species of Passiflora. I had the common red passion-flower growing over the front of my verandah, where it was continually under my notice. It had honey-secreting glands on its young leaves and on the sepals of the flower-buds. For two years I noticed that the glands were constantly attended by a small ant (Pheidole), and, night and day,
Ch. XII.] USE OF HONEY-SECRETING GLANDS.
every young leaf and every flower-bud had a few on them. They did not sting, but attacked and bit my finger when I touched the plant. I have no doubt that the primary object of these honey-glands was to attract the ants, and keep them about the most tender and vulnerable parts of the plant, to prevent them being injured ; and I further believe that one of the principal enemies that they serve to guard against in tropical America is the leaf-cutting ant, as I have noticed that the latter are very much afraid of the small black ants.
On the third year after I had noticed the attendance of the ants on my passion-flower, I found that the glands were not so well looked after as before, and soon discovered that a number of scale-insects had established themselves on the stems, and that the ants had in a great measure transferred their attentions to them. An ant would stand over a scale-insect and stroke it alternately on each side with its antennæ, whereupon every now and then a clear drop of honey would exude from a pore on the back of the scale-insect and be imbibed by the ant. Here it was clear that the scale-insect was competing successfully with the leaves and sepals for the attendance and protection of the ants, and was successful either through the fluid it furnished being more attractive or more abundant. I have, from these facts, been led to the conclusion that the use of honey-secreting glands in plants is to attract insects that will protect the flower-buds and leaves from being injured by herbivorous insects and mammals; but I do not mean to infer that this is the use of all glands, for many of the small appendicular bodies, called “glands” by botanists, do not secrete honey. The common dog-rose of England is fur
nished with glands on the stipules, and in other species they are more numerous, until in the wild Rosa villosa of the northern counties the leaves are thickly edged, and the fruit and sepals covered with stalked glands. I have only observed the wild roses in the north of England, but there I have never seen insects attending the glands. These glands, however, do not secrete honey ; but a dark, resinous, sticky liquid, that probably is useful by being distasteful to both insects and mammals.
If the facts I have described are sufficient to show that some plants are benefited by supplying ants with honey from glands on their leaves and flower-buds, I shall not have much difficulty in proving that many plant-lice, scale-insects, and leaf-hoppers, that also attract ants by furnishing them with honey-like food, are similarly bene. fited. The aphides are the principal ant-cows of Europe. In the tropics their place is taken in a great measure by species of coccidæ and genera of Homoptera, such as Membracis and its allies. My pine-apples were greatly subject to the attacks of a small, soft-bodied, brown coccus, that was always guarded by a little, black, stinging ant (Solenopsis). This ant took great care of the scale-insects, and attacked savagely anyone interfering with them, as I often found to my cost, when trying to clear my pines, by being stung severely by them. Not content with watching over their cattle, the ants brought up grains of damp earth, and built domed galleries over them, in which, under the vigilant guard of their savage little attendants, the scaleinsects must, I think, have been secure from the attacks of all enemies.
Many of the leaf-hoppers-species, I think, of Mem
bracis—were attended by ants. These leaf-hoppers live in little clusters on shoots of plants and beneath leaves, in which are hoppers in every stage of developmenteggs, larvæ, and adults. I believe it is only the softbodied larvæ that exude honey. It would take a volume to describe the various species, and I shall confine my remarks to one whose habits I was able to observe with some minuteness. The papaw trees growing in my garden were infested by a small brown species of Membracis-one of the leaf-hoppers that laid its eggs in a cottony nest by the side of the ribs on the under-part of the leaves. The hopper would stand covering the nest until the young were hatched. These were little softbodied dark-coloured insects, looking like aphides, but more robust, and with the hind segments turned up. From the end of these the little larvæ exuded drops of honey, and were assiduously attended by small ants belonging to two species of the genus Pheidole, one of them being the same as I have already described as attending the glands on the passion-flower. One tree would be attended by one species, another by the other ; and I never saw the two species on the same tree. A third ant, however—a species of Hypoclinea—which I have mentioned before as a cowardly species, whose nests were despoiled by the Ecitons, frequented all the trees, and whenever it found any young hoppers unattended, it would relieve them of their honey, but would scamper away on the approach of any of the Pheidole. The latter do not sting, but they attack and bite the hand if the young hoppers are interfered with. These leaf-hoppers are, when young, so soft-bodied and sluggish in their movements, and there are so many enemies ready to
prey upon them, that I imagine that in the tropics many species would be exterminated if it were not for the protection of the ants.
Similarly as, on the savannahs, I had observed a wasp attending the honey-glands of the bull's-horn acacia along with the ants ; so at Santo Domingo another wasp, belonging to quite a different genus (Nectarina), attended some of the clusters of frog-hoppers, and for the possession of others a constant skirmishing was going on. The wasp stroked the young hoppers, and sipped up the honey when it was exuded, just like the ants. When an ant came up to a cluster of leaf-hoppers attended by a wasp, the latter would not attempt to grapple with its rival on the leaf, but would fly off and hover over the ant; then when its little foe was well exposed, it would dart at it and strike it to the ground. The action was so quick that I could not determine whether it struck with its fore-feet or its jaws; but I think it was with the feet. I often saw a wasp trying to clear a leaf from ants that were already in full possession of a cluster of leafhoppers. It would sometimes have to strike three or four times at an ant before it made it quit its hold and fall. At other times one ant after the other would be struck off with great celerity and ease, and I fancied that some wasps were much cleverer than others. In those cases where it succeeded in clearing the leaf, it was never left long in peace ; for fresh relays of ants were continually arriving, and generally tired the wasp out. It would never wait for an ant to get near it, doubtless knowing well that if its little rival once fastened on its leg, it would be a difficult matter to get rid of it again. If a wasp first obtained possession, it was able