Go Away!

24 November 2020 | Posted in Chris Bentley , Rye Harbour , Wildlife , Insects
Go Away!
Garden Tiger Moth

If, as I do, you run a moth trap you will have noticed that moth colouration falls roughly into two categories. Most exhibit what is called cryptic colouration with dull colours and generally subdued patterns which are designed to act as camouflage and provide protection against predators.  Some go even further; Buff-tip for instance does a rather good impression of a broken twig and Angle Shades looks for all the world like a dead leaf, while species such as Chinese Character (below) and Magpie Moth mimic bird poo! 

 Chinese Character 06

However some, such as the ‘Tigers’ and species such as Cinnabar (both adult and larvae, below) are much more brightly coloured (one might almost say garish in some cases) and not easily missed! The technical term for this colouration is aposematic (the term is derived from the Greek and appears to mean 'a signal to go away'!) and indicates a pretty toxic character. This colouration is mainly designed to work on species with good colour vision (generally birds or reptiles), the idea being that a young and inexperienced predator eats an aposematic creature, is ill, associates the bright colours with feeling awful and remembers not to do it again! The predated individual is dead but the rest of the species have been saved from further attacks from this particular predator.

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Species with warning colouration are often mimicked by other species. If the mimic is also poisonous or venomous this is known as Müllerian mimicry (after the German zoologist Friedrich Müller). Often groups of noxious species will mimic each other, resulting in a ‘mimicry ring’ (bumblebees, below,  are a good example of this). Sharing warning colouration benefits the species in the ring as predators come across the noxious pattern more often and learn to avoid it more quickly. If, on the 

B ruderatus

other hand, the mimic is harmless and is in fact ‘hijacking’ the warning colouration we get Batesian mimicry (after Henry Bates an English explorer/naturalist). Probably the best examples of this in the UK are provided by the hoverflies, harmless insects which mimic either bees or wasps.  This arrangement obviously benefits the mimic which acquires protection on the back of the models noxiousness. The poisonous model, however, actually loses out to a degree as if predators encounter the mimic regularly they will not learn to avoid the warning pattern as quickly as they might. An stunning example of Batesian mimicry is the caterpilar of Elephant Hawk Moth which when threatened does a pretty good impression of a snake, scales and all! (below)

Rxelephant larva

Comments

  • Robin Harris:

    25 Nov 2020 11:44:00

    Good stuff, Chris – a very clear explanation of some of the natural world’s strategies for survival.

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