Friday, February 4, 2011

Warning colours

Soldier bug (Spilostethus pandurus)
Animals with bright colours or contrasting patterns often have an active means of defence that they want to. This is known as warning or aposematic colouration. 

These species do not bother to hide themselves as they advertise the fact that they have an effective mode of defence being either unpalatable or other dangerous. 

Many insects such as several species of bugs and ladybirds have bitter tasting chemicals produced by special glands. Wasps warn potential predators that they have a painful sting.

Predators quickly learn that insects with particular colours or patterns should be left alone. They learn by mistakes which means that some individuals are eaten but their sacrifice is good for the survival of the species as a whole.

Warning colouration is so effective that harmless organisms sometimes mimic harmful animals and use the same colours to defend themselves even though they themselves are not dangerous. 

To be effective the number of mimicking organisms must be much less than that of the unpalatable or dangerous species as otherwise predators would not learn to leave them alone. This type of mimicry is known as Batesian mimicry. 

Another type of mimicry is known as Mullerian mimicry. This occurs when different species of unpalatable or dangerous animals adopt the same colouration thus reinforcing the message and ensuring that fewer individuals need to be sacrificed for predators to learn to leave animals with similar colours or patterns alone.

The soldier bug, known in Maltese as suldat, is a common insect that can be seen running on the ground or at the base of several species of plants. 

At this time of the year it can also be seen on sunny days on a south facing stone or trunk to warm itself up in the early morning sun. It belongs to the suborder Heteroptera (true bugs) which forms part of the order Hemiptera. At first glance it could easily be mistaken for a fire bug another common insect known in Maltese as seffud tal-ġamar, a case of Mullerian mimicry. 

This article was published in The Times on 19.01.11

No comments:

Post a Comment