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Animals with
chemical weapons! USE of chemicals as a means of defence rather than offence, is commonly found in the animal kingdom and and species that are highly colourful are usually those that are possessing chemical weaponry. Animals that produce unpleasant smelling or tasting secretions are generally colourful(warninglycoloured) to advertise their distastefulness. Specially, among insects many species synthesise their own chemical compounds whereas others get them from plants or animals they feed upon. Certain grasshoppers exude repellent substances from their abdomen, and millipedes actually produce hydrogen cyanide from pores along their body. Wasps rely on black-and-yellow stripes to warn of poisonous stings, and many brightly coloured caterpillars advertise their ability to cause irritation and pain if the hairs on their bodies are touched. Larvae of the sawfly
feed on the leaves of pine trees. When threatened, a larva will emit a
drop of fluid from its mouth and daub it over its attacker. This fluid
smells like pine resin and chemical analysis has shown that it is
indeed pine resin. Resin is produced by pine trees for the very
purpose of deterring insects from feeding on them. Most insects cannot
cope with chemical, but a few have become adapted to do so, and the
sawfly larva is one of them. As the insect feeds on pine leaves, the
resin is stored in a pair of pouches in the gut. When it is daubed on
to an insect attacker, the resin acts as a powerful deterrent. Hence,
in this species, a chemical compound produced by a plant to ward off
insects is taken up and used as part of one insect’s own defences. |
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The viceroy caterpillar looks completely
different from that of the monarch and feeds from fairly innocuous plants. But
when the viceroy butterfly emerges, it looks exactly like a monarch. The only
difference is that it does not have the poisons. The viceroy mimics the monarch
in order to confer immunity to attack; and it works. In another monarch
butterflies have been presented to scrub jays. The birds might take one
butterfly, but the reaction is so violent that refuse to touch monarch again.
Presented with the harmless viceroys, the birds behave in the same way. They
will not touch them. |