November 5, 2015

Ground beetles and bushveld lizzards

Beetles are one of the most successful orders on the planet thanks to a holometabolic (complete metamorphosis) lifecycle.  This means that the larva is completely different to the adult in both diet and habitat.  In order to reach adulthood, the larva must undergo pupation before emerging as a beetle (the same mechanism as butterflies and moths).  This theoretically enables them to double the number of individuals in a given area since the problem of competition for space and food is non-existent.  They have also evolved a plethora of anti-predation behaviour essential for survival!

Ground beetles display contrasting colours on their carapace to warn potential predators of their defence mechanisms.  This phenomenon is called aposematic colouration and is essential when their main predator, birds, rely on superb colour vision to hunt.  They are able to squirt a noxious substance at their attackers and are known to be very accurate giving rise to the Afrikaans name ‘oogpisters’ or ‘eye-pissers’!  In some species, the chemicals involved can even burn human flesh. 

Interestingly, there is a reptile found in Southern Africa known called the bushveld lizard that mimics the two-spotted ground beetle shown here.  The juvenile lizards show similar bright markings and even walk with a hunched, slow posture to try and dupe their avian predators.  It is one of the very few examples in nature where an arthropod is mimicked by another class of animals.

Blog written by Ben Coley
Photo courtesy of 
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