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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 furnished 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, and 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 benefited. The aphides are the principal ant-cows of Europe. In the tropics their place is taken in a great measure by species of Coccidce and genera of Homoptera, such as Membracis and its allies. My pineapples 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 any one 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 scale-insects must, I think, have been secure from the attacks of all enemies.
Many of the leaf-hoppers—species, I think, of Membracis—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 development -eggs, larvæ, and adults. I believe it is only the soft-bodied 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-like 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 soft-bodied 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 Hypoclineawhich 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. 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 to keep it; for the first ants that came up were only pioneers, and by knocking these off it prevented them from returning and scenting the trail to communicate the intelligence to others.
Before leaving this subject, I may remark that just as in plants some glands secrete honey that attracts insects, others a resinous liquid that repels them, so the secretions of different genera of the homopterous division of the Hemiptera are curiously modified for strikingly different useful purposes. We have seen that by many species of plant-lice, scale-insects, and leaf-hoppers, a honey-like fluid is secreted that attracts ants to attend upon them. Other species of aphides (Eriosoma) that have no honeytubes, and many of the Coccidæ, secrete a white, flocculent, waxy cotton, under which they lie concealed. In many of the Homoptera, this secretion only amounts to a white powder covering the body, as in some of the Fulgoridæ. In others it is more abundant, and it reaches its extreme limit in a species of Phenax that I found at Santo Domingo. The insect is about an inch in length, but the waxy secretion forms a long thick tail of cotton-like fibres, two inches in length, that gives the insect a most curious appearance when flying. This flocculent mass is so loosely connected with the body that it is difficult to catch the insect without breaking the greater part of it off. Mr. Bates has suggested that the large brittle wings of the metallic Morphos may often save them from being caught by birds, who are likely to seize some portion of the wide expanse of wing, and this, breaking off, frees the butterfly. Probably the long cumbersome tail of the Phenax has a similar use. When flying, it is the only portion of the insect seen; and birds trying to capture it on the wing are likely to get only a mouthful of the flocculent wax. The large Homoptera are much preyed upon by birds. In April, when the Cicadæ are piping their shrill cry from morning until night, individuals are often seen whose bulky bodies have been bitten off from the thorax by some bird. The large and graceful swallow-tailed kite at that time feeds on nothing else. I have seen these kites sweeping round in circles over the tree-tops, and every now and then catching insects off the leaves, and on shooting them I have found their crops filled with Cicadæ.