Metallic-hued ground beetles at Clashmore

May 27th 2017

Several groups of beetles seem to specialise in shiny metallic colours, which often change hue as you view them from different angles. These colours are produced by the reflection of light from the ultra-fine micro-sculpture of their exoskeletons, rather than pigments. The large, brilliant blue, Morpho butterflies found in South America are another example of this phenomenon.

This mating pair of ground beetles was found under a stone at Clashmore Quarry (NC0331) on 11th May 2017. They belong to a species now known as Poecilus versicolor (Pterostichus versicolor in older books), and are about half an inch long. The specific name is curiously apposite, since they can be ‘shining green, coppery, bluish or sometimes black’. In this case the male was both green and coppery; the female (largely invisible in the image) a rather more sober black.

The species is described as ‘generally distributed…in open habitats…in wetter, western areas’, which fits where I found them; nevertheless this appears to be about as far north as the species has been recorded in the British Isles.

Ian M. Evans

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