We accept it or not but the fact remains that insects constitute three-fourth of all animals present on our planet. They are so amazingly ubiquitous that according to one estimate, their population density averages around 500 million per acre. If we do not see them frequently, it is because of their small size and shy nature. Very few people have actually peeped into their amazingly complex ways of living and their extraordinary capabilities.
Insects are six-legged creatures which carry their skeleton outside the body. They are found in all kinds of environs, from frozen antarctica to hotsprings. The great evolutionist Charles Darwin was amazed to find insects on the barren St. Paul`s island off South American coast where otherwise nothing grew. Snowfleas and ladybird beetles in millions can be seen crawling on snow in Himalaya.
Extreme toughness of body can be seen in beetles. Insects are way ahead of all other creatures in running, jumping, swimming and flying. If magnified to the size of human beings, a tiger beetle would run 100 metre in just two seconds and a rat flea will easily clear a bar 200 metre high. Dragonflies, hawk moths and botflies have been known to cruise at an incredible speed of 200 kms per hour. Locust fly slow but can fly non-stop for the whole day without getting exhausted.
Locusts also surpass any other creature in destroying agriculture. An average-sized locust swarm can destroy 60,000 tons of crop in a single day during migration. No wonder in the past locust swarms used to bring famine and large scale deaths.
Termite queen, the most fertile female on earth, lying in her underground Royal chamber lays 30,000 eggs each day and continues to do this job for 30-50 years. This egg-laying machine is actually reproducing at the rate of 2-3 eggs each second–an amazing feat indeed.
Beautiful butterflies add colour to our environment, bumble bees pollinate our crops, and crickets and cicadas sing music in forests. Some insects are obnoxious, some help us in various ways but many more do not bother us at all. We shall explore some of the lesser known aspects of these wonderful creatures in the future episodes of this series.
Ants are cousins of honeybees but while the honeybees are diurnal and sleep in the night, ants are busy working day and night. Ants have no wings and therefore their job of traveling to long distances in search of food is very difficult, but addicted to work as they are and having never-say-die spirit, make them excellent foragers which work round the clock, apparently without any rest.
Ants have the highest developed social system, next only to man, with no apparent conflict seen in the society. Extreme devotion to duty and “Work is worship” attitude binds them together. Like honeybees, castes are specialized, such as queen has large abdomen to lay a lot of eggs, males fertilize her, workers have broad, sharp mandibles for cutting and chewing and the soldiers bear sharp dagger-like mandibles for fighting. Soldiers of door keeping ant (Colobopsis etiolata) have such gigantic heads that they use it for blocking the entrance of the nest. They are extremely powerful creatures that can easily lift 20 times their own weight. They have poor eyesight but have a highly sophisticated chemical language for communication.
Some of the primitive species are hunters; famous among them are Safari ants or Driver ants of Africa and South America, first described by David Livingston in 1853. They are vagabonds moving in large columns of about half a kilometer, with a density of 13 ants per square centimeters. As they move searching every tree, branch and rock of the forest, fear grips the whole area as they attack every animal on their way, covering their bodies in millions and removing chunks of flesh, leaving the skeleton behind within minutes. Even larger animals like monkeys, pythons and deers are demolished by sheer numbers and sharp jaws.
Dairy ants such a Camponotus compressus domesticate aphids called ‘Ant cows’ since they relish their sugary secretion called ‘honey dew’. They keep them in their nests, bring them out in daytime for grazing and protect them from predators.
Some ants are adept at farming. For example, the leaf-cutting ants (Atta) cut pieces of leaves and carry them inside their nests to serve as compost, on which they grow fungus gardens. Farmer ants (Holcomermyx) cultivate choicest grasses outside their nests in well-prepared and manured fields. These crops are protected from pests, de-weeded and harvested, and their seeds stored for the next season. Almost all ants store food for the lean period but in the Australian honey pot ants (Myrmecocystus hortideorum), also called honey barrels or replete, some members are specially modified to store honey. Their bodies are sac-like and appendages modified as hooks. They store honey in their enormously large abdomen and hang from the ceiling and perform no other apparent function.
Slave-making ants described by the renowned entomologists, A.D. Imms and E.O. Wilson seem to have specialized in fighting wars and making slaves from other species of ants, like Formica subsericea. Two species found in South America, namely, Formica subintegra and F. sanguinea organize raids on other colonies to rob them of their food reserves.
Planning of a raid takes several days based on the information gathered by their spies. Inspection of the victim’s colony is done carefully and attack from several directions is normally carried out, giving an element of surprise to the opponent. Propaganda pheromones are released from dufours glands to confuse and demoralize the opponent. The attacked colony is mostly defeated and their granaries robbed. The adults are usually killed but the young larvae are brought to the nest so that they can grow to become slaves and can be used to do menial household jobs.
Close observations on ants reveal a highly developed social system and some of their activities resemble our own, exhibiting a high degree of intelligence. Although they practice a well-marked caste system, there is never a conflict in their society, which is perhaps due to their strong sense of duty.
Termites, commonly known as white ants, are considered to be the most destructive insects to our crops, forests, orchards, timber and houses, a title received by them due to their wood-feeding habit. They are one of those few animal species that survive exclusively on cellulose and carry cellulose-digesting flagellates inside their intestines to help them in this difficult task.
Being shy and photophobous, they make underground nests called termatoria, in which they maintain constant temperature and humidity, even when outside ground temperature rises to above 60 degrees, by constructing intricate over ground natural air conditioners called termite-hills. As the wind passes through the ventilation galleries of the termite hill, the temperature of the nest drops fast.
They never venture out in the open and construct earthen passageways on the trees, walls or on ground and move in the darkness of these tunnels. No wonder their eyes are rudimentary and they communicate almost exclusively in the chemical language. This peculiar underground habitat and shy nature has evolved in them due to a large number of predatory animals like giant anteaters, scaly anteaters, spiny anteaters etc. which exclusively live on termite diet and are always looking for them.
They were the first animals which started living in colonies and developed a well organised social system about 300 million years ago, much earlier than honey bees, ants and human beings. Although termites do not exceed 3-4 mm in size, their queen is a 4 inch long giant that lies in the royal chamber motionless since its legs are too small to move its enormous body. Hence workers have to take care of all its daily chores.
Termite queen is an egg-laying machine that reproduces at the astonishing rate of one egg per second, 24 hours a day and for about 20 years of life. Some Australian species are known to lay up to 60,000 eggs per day. Producing eggs is the only mission in the life of a termite queen. The other castes, workers and soldiers are highly devoted to the colony, working incessantly and tirelessly, demanding nothing in return from the society. Soldiers have long dagger-like mandibles with which they defend their nest and workers chew the wood to feed to the queen and larvae and grow fungus gardens for lean periods.
Nasutes are specialized soldiers which specialize in chemical warfare. They produce a jet of highly corrosive chemical from their bodies that can dissolve the skin of enemies and can also help in making galleries through the rocks. They are bulldozers of the colony. In breeding season which usually coincides with the rains, newly produced males and females grow wings, have nuptial flight, disperse to long distances, make pairs and find a new place to start a colony.
Termites are difficult to eradicate from the houses owing to their hidden activities. They are sensitive to most of the insecticides, and resin producing woods like pine and deodar are known to be resistant to their attack. Timber soaked in dieldrin or aldrin solution is not attacked and soil mixed with the same chemicals keep termites away from houses. Pressure impregnation of wood with creosote or formaldehyde is an effective way of eradicating them, although a termite nest in the neighbourhood is always a constant threat.