Wednesday, November 16, 2011

Hantik - Green Tree Ant: A Classical Case of Social Behavior

Nest of Green Tree Ants
Abe V Rotor

Go to the ant sluggard; consider her ways, and be wise.” (Proverbs, Chapter 6, 6-8)

Hantik!” my friend cried in panic and pain as he hurriedly abandoned the fruit laden mango tree fighting off dozens of golden brown ants clinging on his skin and clothes. He had trespassed into a nest of green tree ants, Oecophylla smaragdina, and now the colony had broken into a swarm. I had my share of the bites and stings as I helped my friend repel the insects. Well, boys are boys, but this gave us a lasting lesson, and for me it opened a door to my career as an entomologist.

Years after when I put up residence in a middle-class subdivision in Quezon City I came across the world of this enigmatic organism once more. This time it came to live with my family. It built nests on two towering trees, ilang-ilang (Cananga odorata) and talisay (Terminalia catappa) which stand on the front yard and across the fence on the sidewalk, their long and thick branches virtually forming one huge crown. There is no escape from the ants; not the garden, the pond, clotheslines and pathways.

No one likes to live with a pest anyway. So I hired a woodcutter who claimed to have been responsible for cutting down some of the oldest balete trees (Ficus benjamina) on ghostly Balete Drive. (Remember the white lady stories?) Armed with bolo and salt allegedly to drive evil spirits, he climbed the talisay tree. Hardly had he began cutting the main branches when the colony of ants broke loose. It was exactly a repeat performance of that incident which happened forty years ago. My plan was abandoned, and I realized my intention was carrying a residue of prejudice.

In the study of insects (entomology), insects are classified into beneficial and destructive species. Honeybees and silkworm are classical examples of the good insects, while the plant-eating and parasitic ones are considered as bad ones. But to ecologists without insects there can be no true balance in the biosphere. What that suggests is the universal idea that every living thing has a place and purpose in this planet. But where does the hantik belong?

It is difficult to pass judgment unless the facts about this insect are presented. Ants are among the most successful evolutionary creatures. They did not only survive millions of years as groups but have, in fact, together with bees, reached the highest evolutionary level - Order Hymenoptera of the largest phylum of animals (Arthropoda). The secret of this success is closely linked with their social life which has fascinated man. Insects inspired autocratic societies, such as those founded on feudalism and dictatorship. Definitely, the caste system where members are categorized according to function, was structured following that of ants, bees and termites.

Basis of Social Behavior

Social scientists and biologists believe that social behavior among living things have a biological basis. The genes which carry the double helix deoxyribose nucleic acid (DNA) control social behavior. That is why social life models somehow follow that of other species. To sociobiologists, led by EO Wilson of Harvard, this is also true with humans. A proof of this is that our history is rich with autocratic cultures and civilizations, among which are the great Egyptian civilization, Roman Empire, Chinese Civilization and other civilizations of the Aztecs, Mayans, and American Indians.

In our age of biotechnology, scientists are looking at the possibility of isolating the gene that controls social behavior in insects which can be spliced into the genes of other organisms in order to make them socially cohesive or adaptable to specific cultural conditions. The same gene may be responsible for dictating the sex of individual organisms and even populations. The basis of this thesis is that worker ants and bees are infertile females, predetermined in their immature stage. With this knowledge, genetic engineering may be able to develop techniques of mass extermination of destructive insects by modifying their sex. Already, in the case of tilapia (plapla), sex reversal (hormonal change) has been the key for preventing overpopulation and competition, and in improving weight gain.

On the practical side, ants are natural predators. They kill other insects, even those much bigger than themselves, as food. Their presence in our yard has caused the disappearance of most garden pest: caterpillars, termites and even other kinds of ants like the red fire ants (Solenopsis geminata rufa) which herd and milk aphids and mealybugs. No, the hantik is not a symbiont of destructive insects of any kind. They are nature’s sweepers and janitors. They carry off morsels and leftovers which would otherwise attract flies and other vermin.

What triggers swarming other than perceived assault? I have seen members coming to the rescue of wounded members, or to carry their dead while the rest is alerted for defense or assault. I have observed advance parties exploring new territories, ants that tap the nest to warn the colony of danger, and those which weave nests by clamping the edges of leaves together, and fastened with a sticky secretion of larvae.

When the prey is big, an army is set in place to tear it down in due time. In peaceful times members form a column toward a food source, each carrying a bit to their granary. But always, there is the courteous “kissing”, their antennae tapping and touching, mandible-to-mandible, or head-to-hind, and all in some kind of frenzy and spontaneity. Pheromone, the chemical that binds members and the royalty (queen) together, is transferred and shared this way.

According to Klaus Dumpart of JW Goethe University, several substances work together in raising alarm. One alarm triggering secretion comes from the mandible gland which includes hexanol. Just the scent of this complex substance can be picked up and interpreted by the members. Apart from this secretion, formic acid is secreted by the Dufour gland found at the posterior part of the abdomen. It serves both as pheromone and poison. The ant injects this poison into the victim when it stings. To paralyze a prey or fight an enemy, an ant bites tenaciously with a pair of huge mandibles, while at the same time, injecting poison with a retractable needle at its posterior end.

Extracts from the glands of ants and bees are useful in medicine for the cure of arthritis and rheumatism. Although induced stinging on affected area of the skin and joints of people suffering of acute arthritis is not new, the growing popularity of alternative medicine has even made the practice available in a number of US hospitals and clinics.

It is interesting to know that the eggs and larvae of hantik are gathered for food (it is cooked adobo style), and it is claimed to be an aphrodisiac, according to barrio folk in Abra. This is also a common practice in tropical rainforests in Asia and in the savannahs of Africa where these ants abound.

I look back the nest of the hantik ants without culinary designs nor a residue of a past painful experience, and I think of them now as good neighbors. If, for any reason I receive a sting or two, I complain not, for I believe that sting is good for the heart. Hantik ants prove to be very friendly and cooperative. Pavlov is right after all. ~

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