Olama. The “Sanate.” Muy-muy. Idleness of the people. Mountain road. The “Bull Rock.” The bull’s-horn thorn. Ants kept as standing armies by some plants. Use of honey-secreting glands. Plant-lice, scale-insects, and leaf-hoppers furnish ants with honey, and in return are protected by the latter. Contest between wasps and ants. Waxy secretions of the homopterous hemiptera.
WE rode up to the large hacienda at Olama, and were asked to alight by a man whom I at first took to be the proprietor, but afterwards discovered to be a traveller like ourselves, buying cattle for the Leon market. The owner of the house and his sister were away at a little town three or four miles distant; and I was a little nervous about the reception we should have when they returned and found us making ourselves at home at their house. Velasquez had, however, no apprehensions on that score, as he knew that throughout the central departments of Nicaragua it is the custom for travellers to expect and to receive a welcome at any house they may arrive at by nightfall. Excepting in the towns, and on some of the main roads, there are no houses where travellers can stop and pay for a night’s lodging. Every one expects to be called on at any time to give a night’s shelter. This is all that is afforded, as travellers carry with them their hammocks and food. About an hour after dark, the owner and his sister returned on mules, and the gentleman seemed pleased at finding us at his house. I was about to offer a chair to the sister; but Velasquez told me it was not the custom to show any civilities to the ladies, as they would probably be misconstrued. After a while, the master had some chocolate brought to him by his sister, who waited upon him. The wife, the sister, and the daughter in the departments seldom sit down to their meals with the master of the house, but attend upon him like servants.
Whilst coffee was preparing next morning, I strolled about the outbuildings, and was much amused at the antics of the jet black Quiscalus, called “sanate” by the natives. They are about the size of a magpie, with much of the active movements of that bird. They are generally seen about cattle, sometimes picking the garrapatos off them, but more often one on each side, watching for the grasshoppers and other insects that are frightened up as the cattle feed. On this morning there were several of them on the top of a shed. Every now and then one would ruffle out its feathers, open its wings a little, give a step or two forward towards another, stretch out its neck, open its bill, and then give rather a long squeak-like whistle. As soon as it had done this, it would hurriedly close its feathers and wings, and hold its head straight up, with its bill pointing to the sky. All its movements were grotesque; and its sudden change in appearance after delivering its cry was ludicrous. It appeared as if it was ashamed of what it had done, and was trying to look as if it had not done it — just as I have seen a schoolboy throw a snowball, and then stand rigidly looking another way. After a few moments, the “sanate” would lower its head, and, in a short time, go through the same performance again, repeating every movement automatically.
Bidding adieu to our host, we rode over grassy savannahs, with much cattle feeding on them, and in about five miles reached a small village called Muy-muy, which means “very-very.” I think it is a corruption of an old Indian word “Muyo,” met with in other Indian names of towns, as, for instance, in Muyogalpa. After riding all round the plaza, which formed three-fourths of the town, we at last found a house where they consented to make us some tortillas, on condition that we would buy some native cheese also. The land around was fertile, but the people too lazy to cultivate it. Many of the houses were dilapidated huts. The place altogether had a most depressing aspect of poverty and idleness. I asked one man what the people worked at. He said, “Nada, nada, senor,” that is, “Nothing, nothing, sir.” Some of them possess cattle; and those that have none sometimes help those that have, and get enough to keep them alive. The principal subject of interest seemed to be the “caritos,” who had come up the river and given them guns and iron pots for their black dogs; but no one had had the curiosity to ask what they wanted the dogs for. It was Sunday, and many of the country people from around had come into the village. All that had any money were at the estanco, drinking aguardiente. The men were dressed alike, with palm-tree hats, white calico jackets and trousers, the latter often rolled up to the thigh on one leg, as is the fashion in this part of the world. Nearly all were barefooted.
Having breakfasted off tortillas and cheese, we continued our journey, and crossed two rivers running to the eastward; then ascended a high and rocky range, along the top of which the path lay. We took this mountain-path to avoid some very bad swamps that we were told we should encounter if we went by the main road. The mountain range was bare and bleak, but we had a fine view over the surrounding country. Opposite to us, on the other side of a wide valley, was a similar range to that along which we were travelling, the sides partly wooded and partly cleared for planting maize. We passed several Indian huts with grass-thatched roofs, and met a party of Indians travelling down the mountain in single file, each man carrying his bow and arrows. They were going down to Huaco to buy corn, the maize crop having failed around Matagalpa the last season. The mountain road, though dry, was rocky, with steep ascents, and our mules got very tired. About five o’clock we descended from the hills into the valley of Ocalca, near to which there had been some gold workings, now abandoned. Here we came in sight, for the first time, of the pine forests, a high range a few miles to the north being covered with them.
About dusk, we reached an Indian hut, and proposed staying there for the night. The owners were pure Indians; the women, engaged as usual in grinding maize, were naked to the waist. There was an old man and his son, and some children. The old Indian looked distressed at our proposal to take up our quarters there for the night, but he made no objection. The accommodation was very poor, there being no hammocks or bedsteads; and I think all the inmates must have slept above on some bamboos that were laid across the beams. Learning from the old man that there was a large and better house a little further on, we relieved him of our company, and crossing a river, reached a cattle hacienda owned by a very stout native named Blandon, who made us welcome. The house was a large one; and there were a number of mozos and women-servants about. We asked if we could buy anything to eat, and Senor Blandon said he would get supper prepared, at which we were much pleased, as we had had nothing all day excepting a drink of coffee at daylight, and some tortillas and cheese at Muy-muy. After waiting a long time, we were invited to our supper; and on going into an inner room, found it consisted only of coffee and two small cakes called “roskears” for each of us; and we were told they had nothing else to offer us. So, munching our dry roskears, we mumbled over them as long as we could, and did not waste a crumb, wondering how our host got so fat on such fare. We were as hungry when we finished as when we began, and soon laid down on our hard couches to forget our hunger in sleep.
We started off early the next morning, as we were within a few leagues of the town of Matagalpa, and knew when we got there we should obtain plenty of provisions. About a league before arriving at Matagalpa there is a high range, with perpendicular cliffs near the summit. Rito told us that near the base of these cliffs there was a carving of a bull, and that the place was enchanted. I had heard in other parts stories of bulls being engraved or painted on rocks, but was very doubtful about their being true, as, up to the advent of the Spaniards, the Indians of Central America had never seen any cattle; and since the conquest they appear to have entirely given up their ancient practice of carving on stone, whilst the Spaniards and half-breeds have not learnt the art; so that I have never seen a single carving in the central departments that could be ascribed to a later period than the Spanish conquest.
Tired and hungry though we were, I was determined to put this story to the test; so Velasquez and I climbed up to the cliffs, and searched all round them, but could find no carving. At one place there was a large black stain on the cliff, produced by the trickling down of water from above, and I afterwards learnt that this stain at a distance somewhat resembled a bull, and a little imagination completed the likeness. The lady of the house where we stayed at Matagalpa assured us she had seen it, and that everything appertaining to a bull was there. This she insisted on with a minuteness of detail rather embarrassing to a fastidious auditor.
Clambering down the rocks, we reached our horse and mule, and started off again, passing over dry weedy hills. One low tree, very characteristic of the dry savannahs, I have only incidentally mentioned before. It is a species of acacia, belonging to the section Gummiferae, with bi-pinnate leaves, growing to a height of fifteen or twenty feet. The branches and trunk are covered with strong curved spines, set in pairs, from which it receives the name of the bull’s-horn thorn, they having a very strong resemblance to the horns of that quadruped. These thorns are hollow, and are tenanted by ants, that make a small hole for their entrance and exit near one end of the thorn, and also burrow through the partition that separates the two horns; so that the one entrance serves for both. Here they rear their young, and in the wet season every one of the thorns is tenanted; and hundreds of ants are to be seen running about, especially over the young leaves. If one of these be touched, or a branch shaken, the little ants (Pseudomyrma bicolor, Guer.) swarm out from the hollow thorns, and attack the aggressor with jaws and sting. They sting severely, raising a little white lump that does not disappear in less than twenty-four hours.
These ants form a most efficient standing army for the plant, which prevents not only the mammalia from browsing on the leaves, but delivers it from the attacks of a much more dangerous enemy — the leaf-cutting ants. For these services the ants are not only securely housed by the plant, but are provided with a bountiful supply of food, and to secure their attendance at the right time and place, the food is so arranged and distributed as to effect that object with wonderful perfection. The leaves are bi-pinnate. At the base of each pair of leaflets, on the mid-rib, is a crater-formed gland, which, when the leaves are young, secretes a honey-like liquid. Of this the ants are very fond; and they are constantly running about from one gland to another to sip up the honey as it is secreted. But this is not all; there is a still more wonderful provision of more solid food. At the end of each of the small divisions of the compound leaflet there is, when the leaf first unfolds, a little yellow fruit-like body united by a point at its base to the end of the pinnule. Examined through a microscope, this little appendage looks like a golden pear. When the leaf first unfolds, the little pears are not quite ripe, and the ants are continually employed going from one to another, examining them. When an ant finds one sufficiently advanced, it bites the small point of attachment; then, bending down the fruit-like body, it breaks it off and bears it away in triumph to the nest. All the fruit-like bodies do not ripen at once, but successively, so that the ants are kept about the young leaf for some time after it unfolds. Thus the young leaf is always guarded by the ants; and no caterpillar or larger animal could attempt to injure them without being attacked by the little warriors. The fruit-like bodies are about one-twelfth of an inch long, and are about one-third of the size of the ants; so that an ant carrying one away is as heavily laden as a man bearing a large bunch of plantains. I think these facts show that the ants are really kept by the acacia as a standing army, to protect its leaves from the attacks of herbivorous mammals and insects.
The bull’s-horn thorn does not grow at the mines in the forest, nor are the small ants attending on them found there. They seem specially adapted for the tree, and I have seen them nowhere else. Besides the Pseudomyrma, I found another ant that lives on these acacias; it is a small black species of Crematogaster, whose habits appear to be rather different from those of Pseudomyrma. It makes the holes of entrance to the thorns near the centre of one of each pair, and not near the end, like the Pseudomyrma; and it is not so active as that species. It is also rather scarce; but when it does occur, it occupies the whole tree, to the exclusion of the other. The glands on the acacia are also frequented by a small species of wasp (Polybia occidentalis). I sowed the seeds of the acacia in my garden, and reared some young plants. Ants of many kinds were numerous; but none of them took to the thorns for shelter, nor the glands and fruit-like bodies for food; for, as I have already mentioned, the species that attend on the thorns are not found in the forest. The leaf-cutting ants attacked the young plants, and defoliated them, but I have never seen any of the trees out on the savannahs that are guarded by the Pseudomyrma touched by them, and have no doubt the acacia is protected from them by its little warriors. The thorns, when they are first developed, are soft, and filled with a sweetish, pulpy substance; so that the ant, when it makes an entrance into them, finds its new house full of food. It hollows this out, leaving only the hardened shell of the thorn. Strange to say, this treatment seems to favour the development of the thorn, as it increases in size, bulging out towards the base; whilst in my plants that were not touched by the ants, the thorns turned yellow and dried up into dead but persistent prickles. I am not sure, however, that this may not have been due to the habitat of the plant not suiting it.
These ants seem at first sight to lead the happiest of existences. Protected by their stings, they fear no foe. Habitations full of food are provided for them to commence housekeeping with, and cups of nectar and luscious fruits await them every day. But there is a reverse to the picture. In the dry season on the plains, the acacias cease to grow. No young leaves are produced, and the old glands do not secrete honey. Then want and hunger overtake the ants that have revelled in luxury all the wet season; many of the thorns are depopulated, and only a few ants live through the season of scarcity. As soon, however, as the first rains set in, the trees throw out numerous vigorous shoots, and the ants multiply again with astonishing rapidity.
Both in Brazil and Nicaragua I paid much attention to the relation between the presence of honey-secreting glands on plants, and the protection the latter secured by the attendance of ants attracted by the honey. I found many plants so protected; the glands being specially developed on the young leaves, and on the sepals of the flowers. Besides the bull’s-horn acacias, I, however, only met with two other genera of plants that furnished the ants with houses, namely the Cecropiae and some of the Melastomae. I have no doubt that there are many others. The stem of the Cecropia, or trumpet tree, is hollow, and divided into cells by partitions that extend across the interior of the hollow trunk. The ants gain access by making a hole from the outside, and then burrow through the partitions, thus getting the run of the whole stem. They do not obtain their food directly from the tree, but keep brown scale-insects (Coccidae) in the cells, which suck the juices from the tree, and secrete a honey-like fluid that exudes from a pore on the back, and is lapped up by the ants. In one cell eggs will be found, in another grubs, and in a third pupae, all lying loosely. In another cell, by itself, a queen ant will be found, surrounded by walls made of a brown waxy-looking substance, along with about a dozen Coccidae to supply her with food. I suppose the eggs are removed as soon as laid, for I never found any along with the queen-ant. If the tree be shaken, the ants rush out in myriads, and search about for the molester. This case is not like the last one, where the tree has provided food and shelter for the ants, but rather one where the ant has taken possession of the tree, and brought with it the Coccidae; but I believe that its presence must be beneficial. I have cut into some dozens of the Cecropia trees, and never could find one that was not tenanted by ants. I noticed three different species, all, as far as I know, confined to the Cecropiae, and all farming scale-insects. As in the bull’s-horn thorn, there is never more than one species of ant on the same tree.
In some species of Melastomae there is a direct provision of houses for the ants. In each leaf, at the base of the laminae, the petiole, or stalk, is furnished with a couple of pouches, divided from each other by the mid-rib, as shown in the figure. Into each of these pouches there is an entrance from the lower side of the leaf. I noticed them first in Northern Brazil, in the province of Maranham; and afterwards at Para. 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 on one sickly-looking plant at Para. In many of the pouches I noticed the eggs and young ants, and in some I saw a few dark-coloured Coccidae 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. My subsequent experience 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 benefiting 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 Coccidae 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, 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 is 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 observed 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 antennae, whereupon every now and then a clear drop of honey would exude from a pore on the back of the latter 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.1 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 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.
1 I have since observed ants attending scale-insects on a large plant of Passiflora macrocarpa in the palm-house at Kew.
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 Coccidae 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, larvae, and adults. I believe it is only the soft-bodied larvae 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 larvae 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 leaf-hoppers. 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 honey-tubes, and many of the Coccidae, 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 Fulgoridae. 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 Cicadae 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 Cicadae.
The frog-hoppers, besides exuding honey in some genera and wax in others, in a third division emit, when in the larval state, a great quantity of froth, in which they lie concealed, as in the common “cuckoo-spit” of our meadows.
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