Omnipresent Ants

Ants, constituting the insect family Formicidae, are a large group. According to the great American entomologist E. O. Wilson, 11,574 species of ants have been discovered and named (Holldobler and Wilson, 1990; Wilson, 2003). Many more species remain unrecorded. When all the species will be discovered and described, their number will probably come close to 20,000. Like the humans they are found in almost all parts of our planet. They are there in peripheral parts of the polar regions, and in the rest of terrestrial areas, including deserts, tropical forests, grasslands, sea shores and at high altitudes on mountains. Hence to call them omnipresent is only an excusable exaggeration. Ants are missing in the Arctic, including Greenland, and Antarctic, where there is no food and it is too cold.

In frigid areas of Alaska and north Canada they are plant feeders, and help in pollinating flowers. Away from these extreme north areas, they may derive their nourishment from plants, but they do not act as pollinating agents, as they possess glands, which kill pollens (Jolivet, 1991). However, they are known to pollinate orchids in Australia. Ants have not been found so far in Greenland, but they may be discovered in future. According to the high altitude expert M. S. Mani (1974), the common high altitude ants are species of Formica, Cataglyphis and Campono-tus. He collected Formica picea at the height of 4800 m on the north-west Himalayas.

Desert ants show remarkable adaptations to their arid surroundings. They make deep subterranean nests, consisting of a complex system of galleries and chambers. At a certain depth in soil, there is some moisture, there are no such violent temperature changes as on the ground surface and moist soil particles are held together more firmly giving some permanency to the ants' abode. The soil, removed during digging and making of the nest, is arranged as a little heap on the ground surface with mouth of the nest appearing as a crater on it.

A special feature of the life of ants in a desert area is the habit of collecting and storing food during the brief period of vegetation growth, when some food is available in the arid habitat, so that food is there for members of the colony throughout the year.

Among desert ants are harvester ants, which store seeds of various grasses in the nest in some special chambers, which may be called granaries. Vigorous seed gathering is done towards the end of the growing season. One interesting fact about the life of harvester ants is that there may be wars between members of two colonies of the same species. Winners in a war take away the stored grains from the losers' nest to their own. True wars (i.e. organized conflicts between two conspecific groups) are known only in two members of the Animal Kingdom, namely ants and humans. The great zoologist-philosopher Julian Huxley has pointed out that accumulation of property seems to have led to wars both in ants as well as in man. In human history wars are believed to have started after man took to settled life with agriculture and habit of storage.

Some arid area ants are known to store sugary fluid, collected from plants in the brief period of plant availability, within the body of some workers, which act as living banks of reserve food or 'repletes'. Such ants are known to occur in deserts of South America, Mexico, parts of USA, Africa and Australia. As in case of other ants, the honey storing ants are markedly polymorphic. A colony of honey hoarding ants consists of a queen and workers, amongst which are nurses, guards, honey collectors and honey pot ants or repletes. The honey pot ants are workers, which are set aside by nurses, when the former are quite young, and their skin and gut wall are still soft and pliable. During a small period of vegetation growth the honey collectors dexterously drink in liquid nourishment from flowers of cacti, other desert flowers and galls of certain plants. With their swollen abdomens, distended with the collected juices, they return to their nest and reach the chambers with repletes. The repletes or the honey pot ants have their legs dug into the soft roof of these chambers, and they are hanging from the roof. Here the honey gatherers regurgitate drop by drop most of their liquid gut contents close to the mouth of the repletes. The repletes readily engulf those drops. Thus by mouth to mouth transfer most of the food, collected by the gatherers, enters the gut of the repletes. The abdomen of the latter increases several times the original size due to accumulation of liquid nourishment in their guts. The honey storing repletes never move out from the nest, and they have sacrified their individuality for the purpose of food storage for the colony (Poole and Poole, 1963). In dry periods, when no food is available in the surroundings, the inmates of the colony survive on the liquid droplets emerging from the mouths of repletes, when they are stimulated by stroking with antennae of the hungry sisters.

Elsewhere in temperate, subtropical and tropical regions there is an abundance of ant species. They mostly make their nests in the form of subterranean galleries and chambers or under stones and logs. Many ants arrange the dug out earth at the mouth of their underground nests, forming a little hillock. Of special interest are carpenter ants, which make their nest by boring into wood. Some carpenter ants make their way into the narrow space between bark and trunk wood. Using their strong jaws they make their galleries in the hard wood. Some others burrow into rotting wood or wood softened by and already excavated by wood boring beetles. Ants on sea shores and river banks live on drift wood and other organic debris available there.

Tropical and subtropical ants take to some amazing ways of nest making. Some of them make hanging nests on trees with leaves "tailored" together. Their nest making activity has been described in the Chapter 11. "Insect and Tools". Some tropical ants make a flower garden up on a tree. They carry bits of moist earth from the forest floor to a point of forking in a tree limb. Through long and continuous hard work of the ants the earthy deposit takes the shape of a fairly large ball. The ants now start bringing up seeds of the various plants on the forest floor, and putting them into the mud ball. After some time the ball becomes covered with flowering vegetation. While the vegetation is growing, the ants dig galleries and chambers in the mud ball. The vegetation cover makes the earthy ball resistant to the tropical rains. According to Seidel et al. (1990), some of the volatile compounds on seeds of ant-garden epiphytes probably play a role in attracting ants to the epiphyte seeds (Jolivet, 1998). It has been questioned by some authors: why do ants make their hanging gardens? Perhaps the attractants present on epiphyte seeds invite them to do so.

Ant-plants or myrmecophytes are plants which offer to ants natural housing facilities, to be used as a nest and eventually as latrines, and, often, but not always, food in various forms (food bodies or trophosomes, pearl bodies, extra-floral or floral nectaries, edible fruits, elaiosomes or seed outgrowths, containing fats or oils, pith in the stem, saprophytic fungi, oil droplets, etc.). In exchange, the ants are supposed to defend the plant against phytophagous insects and mites, feed it through their excreta and cadavers, prune the climbers and the weeds, reject the eggs of parasites, etc. Sometimes the sugars, supplied by coccids and other homopterans, replace what the ant gets directly from the plant. Lodging for the ants is named as domatia. Domatia have been defined as plant-produced chambers that house animals, e.g. the ants, differing from the galls in that they are not induced by their inhabitants. Domatia can lodge also mites or thysanoptera. They are not exclusive habitats for ants. Ant domatia are usually in hollow stems, stipular horns, petioles, hypocotyle axis, pseudob-ulb, rarely in roots, and also in hollow leave spaces.

Many myrmecophytes are known, more than 510 species, belonging to 65 plant families, around 277 in America (23 families), 66 in Africa (14 families) and 167 (28 families) in Asia and Oceania. Several new myrmecophytic plant families are being discovered in SE Asia and more remain to be described, specially in New Guinea and Borneo. There are myrmecophytes in Northern Australia, but none in New-Caledonia and New-Zealand. None exists also in temperate regions, except perhaps one case in Texas. Their structure is generally preadapted and hollow to harbour ants, but in a few of them the ants dig themselves into the pith. Others have special adaptations in the leaves (leaf pouches or domatia), like the Tococa and Maieta, and many more Melastomataceae, in America. Some myrmecophytes eventually grow even into the ant-gardens (Jolivet, 1996). Some are remarkable myrmecophytes, like Myrmecodia and Hydnophytum, in SE Asia, with preformed and specially aerated cavities, some absorbing excreta and cadavers of the inhabiting ants (e.g. Philidris myrmecodiae).

Ants are very variable in their feeding habit. They may be phytophagous, carnivorous or saprophagous. In chapter 39. "Aphids and Ants", ants using aphids for feeding on plant juices have been described. Many ants are fungivorous. They grow fungi in some chambers of their nest. The parasol ants use bits of leaves and their own excreta as the substrate in their fungal garden (see chapter 35, "Parasol Ants"). Other fungus cultivating ants are known to use caterpillars' excreta, fallen anthers of flowers and other soft plant debris for this purpose.

A considerable part of the dispersal of ants across the world has been due to human activities. Ants have been moving with boats, wagons and timber. Entomologists sometimes take to fanciful thinking. They have imagined that, when man is able to establish his covered colonies on the moon or on the Mars, ants will accompany him there. At the moment ants are almost omnipresent on the Earth and new invaders like Solenopsis, Wasmannia are slowly extending their area.

The ants' great adaptability, well pronounced polymorphism (i.e. occurrence of adult individuals with different forms and capability), wide range of food choice, a fine distribution of labour in an ants' colony, and their close association with some articles of human use are the factors responsible for their almost universal distribution.

— Fig. 5.1. Philidris (—Iridomyrmex) myrmecodiae, ant living inside Myrmecodia spp. in SE Asia.

— Fig. 5.2. Neotropical Acacia, Mexico. A: swollen stipules or thorns, harbouring ants; B: nectaries on the petiole; C: Beltian food bodies or trophosomes at the end of the folioles (after many authors and Jolivet, 1996).

— Fig. 5.3. Oecophylla workers building a nest in joining the leaves and using larvae as shuttle (after Dumpert, 1981).

— Fig. 5.4. An ant-garden in Guyana, on a tree (after Jolivet, 1996).

10 mm

5 mm

5 mm

10 mm

5 mm

— Fig. 5.5. a: View of Hoffmannia vesiculifera (Rubiaceae) leaf (abaxial view) showing location of the formicaria on the petiole; b: a lateral view of the vesicle with a portion of the wall cut away; c: three cross-sections through the vesicles. P: lipid glands; R: refuse deposits (after Windsor and Jolivet, 1996).

— Fig. 5.6. Hoffmannia vesiculifera Standley. A: a twig; B: flower; C: fruit. (after Dwyer, 1980). Panama.

10 mm
5 mm

— Fig. 5.7. Triplaris sp. (Polygonaceae), from the Pantanal, Mato Grosso, Brazil, inhabited by ferocious ants, mostly Pseudomyrmex spp. (after Benson, 1984).

— Fig. 5.8. a: a single Besleria formicaria (Gesneriaceae) leaf; b: five cross-sectional views of the leaf along the formicaria (after Windsor and Jolivet, 1996).

— Fig. 5.9. Hoffmania vescicularia (Rubiaceae), Panama (photo Jolivet).

— Fig. 5.10. Hoffmania vescicularia, — Fig. 5.11. Besleria formicaria

Panama. Section through the domatia (Gesneriaceae), another myrmecophyte

(photo Jolivet). from Panama (photo Jolivet).

— Fig. 5.12. Myrmecodia sclechteri Valeton (Rubiaceae), epiphytic on Casuarina nodiflora. Goroka, New Guinea (photo Jolivet).

— Fig. 5.14. The same as Fig. 5.12, median section of the inflated tubercles (hypocotyle axis) showing the cavities occupied by the ants (Philidris spp.) and some internal roots (photo Jolivet).

— Fig. 5.16. Cordia alliodora (Boraginaceae) with an opened node containning the ants (Azteca), Panama (photo Jolivet).

— Fig. 5.13. The same as Fig. 5.12, detail of leaves and fruits (photo Jolivet).

— Fig. 5.15. Acacia collensii (Legum. Mimosaceae), Panama, harboring Pseudomyrmex ants in the stipular spines. Extrafloral nectaries and Beltian bodies are visible (photo Jolivet).

— Fig. 5.17. The same as Fig. 5.16. at a higher magnification (photo Jolivet).

— Fig. 5.18. Diagram of a vertical cut through the subterranean nest of an arid area ant. Dots are intended to show moisture in soil.

— Fig. 5.19. Three types of workers in a colony of a myrmicine ant. (soldier — a large worker with extra large head and mandibles; macrergate — a large bodied worker; micrergate — a small bodied worker).

References

Benson, W W 1985. Amazon Ant-Plants. In France, G. T. and Lovejoy, T. E. (eds.).

13. Pergamon Press, Oxford: 239-266. Dumpert, K. 1981. The Social Biology of Ants. Pitman Publishing Lim., Boston: 298 pp. Dwyer, J. D. 1980. Rubiaceae. Part I. In Flora of Panama. Ann. Miss. Bot. Gardens 67 (1): 222-245.

Hölldobler, B. and Wilson, E. O. 1990. The Ants. Harvard University Press,

Cambridge, Mass., USA : 732 pp. Jolivet, P. 1986. Les Fourmis et les Plantes. Un exemple de Coévolution. Boubée publs., Paris : 254 pp. Jolivet, P. 1991. Curiosités Entomologiques. Chabaud, Paris. Jolivet, P. 1996. Ants and Plants. An example of coevolution. Backhuys Publs., Leiden, Holland.

Jolivet, P. 1998. Interrelationship between Insects and Plants. CRC Press, Boca Raton, FL, USA.

Mani, M. S. 1974. Fundamentals of High Altitude Biology. Oxford and IBH Publishing, Bombay.

Poole, L. and Poole, G. 1963. Weird and Wonderful Ants. Heinemann, London. Seidel, J. L., Epstein, W W and Davidson, D. W 1990. Neotropical ant Gardens.

I.Chemical constituents. J. Chemic. Ecology 16 (6): 1791—1816. Wilson, E. O. 2003. Pheidole in the New World. A dominant, hyperdiverse ant genus.

Harvard University Press, Cambridge, Mass. USA. Windsor, D. M. and Jolivet, P. 1996. Aspects of the morphology and eciology of two Panamanian ant-plants, Hoffmannia vesciculifera (Rubiacea) and Besleria formicaria (Gesneriaceae). Journal of Tropical Ecology 12: 835-842.

0 0

Post a comment