Surviving the bitter cold

Last Sunday’s sunshine and the relatively warm temperature was welcome especially after the cold wet days that we had been experiencing throughout most of this month. 

As I do on most Sundays I spent the morning photographing nature. I was not expecting any insects but was surprised to see a solitary asphodel bug (seffud tal-berwieq). 

This species which is usually seen from March to May is found mostly on asphodels. It was standing motionless on a leaf trying to warm up its body. It did not move away when I moved very close to it with my camera. 

This was not surprising as even though the low winter temperatures made it lethargic it normally does not bother to conceal itself or run away from danger as like other brightly coloured insects it felt secure in the knowledge that predators, especially birds are unlikely to harm it. Predators learn that animals with warning colours are inedible because they are either foul-tasting or poisonous.  

The presence of this insect made me think about how insects and other animals survive the winter. Many birds avoid cold weather by migrating to warmer parts of the world but in Europe very few insects migrate and their journeys are not as long and regular as those of birds. 

Some adult insects find a sheltered place usually underneath a stone or bark or in a crack in which to spend the winter. Others die as soon as the weather starts to cool but leave behind them eggs or pupae which will continue their lifecycle with the onset of warmer weather.

Malta’s only amphibian, the painted frog remains active throughout the winter as this is also the time when water, which is essential for this animal to survive, is present but the reptiles including the lizard, geckos and chameleon are inactive throughout most of the winter and venture out only on warmer days.

This article was published in The Times on 15.02.2012.

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