Their jaws have two pincers for grasping; on their heads, a pair of antennae serve as sensory organs for feeling and smelling; six legs and a skinny jointed waist complete the picture of one of nature's most efficient designs - the insect. There are countless species of insects, and new ones are named every year. The insect's body model is very adaptable, and its wide distribution is largely due to a social system which puts the colony rather than the individual in the foreground.
Colonial Life
If we could enter a termite mound, it would be like passing through the doors of a huge fortress, a labyrinth or even a skyscrapper, for some Africa species build towers up to 7m high. Inside is a network of walkways and chambers, the layout of which guarantees co-operation within the community. Termites even build an efficient ventilation system which allows the carbon dioxide exhaled by thousands of colony members to excape. However, you would look in vain if you tried to find the master builder who planned the structure. No individual directs any f the colony's actions - except the group itself.
Termites are blind from birth and lack individual intelligence. However, as a community they are brilliant builders. Together with ants, bees and wasps, they belong to the group of insects which forms colonies and whose behaviour fascinates researchers. Scientists see in the behaviour of these insects many similarities to human societies - including hierarchical structures, with queens, drones or kings, workers and soldiers. For a long time, researchers thought that insect colonies functioned so well because the actions of individuals were controlled by instinct - built-in patterns of behaviour. In recent years, attention has focused on chemical substances called pheromones, which, when released into an animal's surroundings, influence the behaviour or development of other individuals of the same species.
Chemical Messages
A termite mound starts to take shape when workers of the species Bellicositermes form little mud balls, mix them with saliva and then arrange them in small piles, apparently at random. Since the scent of saliva is strong, the termites make their mounds increasingly larger, and they eventually tower chimneylike towards the sky. If two columns are close together, the workers at the top of one chimney may become attracted by the pleasant scent of the neighbouring structure. Piles of earth are built up between them to make a rudimentary bridge, which is soon reinforced to form an arch.
The whole process takes place without an architect, manager or central programme, a phenomenon that scientists have dubbed the 'ping-pong effect'. To put it another way, the work influences the worker, and vice versa. although this explanation does not shed light on all the phases that are involved - especially the construction of the queen's chamber or the hard outer wall of the termite hill - it indicates the importance of chemical substances in the exchange of information between individuals. Without these chemical signals, there would be no community life. In a bechive, for example, the queen secrets a specific phenomone that renders the worker bees infertile by retarding the development of their ovaries. By licking the queen bee, the other bees absorb the chemical substance and spread it, guaranteeing that the queen will be the only one capable of sproducing.
Individual Scents
Chemistry also explains how ants tell each other about food supplies. If one of them finds food, it secretes a pheromone from its abdomen, which then marks the way to the ant hill. As soon as another ant crosses this path, it will react in a similar manner. Soon, the little scent trail becomes a wide river.
Pheromones also enable insects to detect infividuals of the same group. A termite, for example, uses its feelers, which are covered with smelling cells, to test the cuticle - the waxy outer layer covering the epidermis of insects - of all it meets. The exoskeleton of each type of termite, and of each individual colony, has a distinctive smell, which comes from specific carbohydrate molecules that form the suticle.
Social Insects
With the exception of humans, no other species has matched the achievements of the social insects - for example, the leaf-cutting ants of the species Atta. These industrious creatures cut and remove parts of leaves, and take them back to the colony, where they are used to raise crops of fungi. No other animal, not even the most intelligent ape, can tell another member of the species the direction where food is to be found and how far away it is. The honey bee holds this honour - thanks to their famous 'waggle' dances, first described in the 1920s.
0 comments:
Post a Comment