Saturday, 4 July 2009

Blue beetles on Artichokes - Hoplia coerulea.

Hoplia coerulea
It was an astonishing sight to see these brilliant blue jewels of beetles sitting on the leaves of Topinambour (the Jerusalem artichoke), in June.  A photo of a specimen does not reflect the incredible iridescence that comes with the sun shining on the surface structure of the beetle. For the colour is not within the substance of the surface but is formed by the refraction of the light as with a prism. In contrast the legs and underside shine like silver.
Several of these beetles were sitting immobile of the leaves. All were males. The females are apparently less often seen and are a muddy brown.  I read that in museum collections of this species there is only one female to every thousand males.  The males will sit on a leaf and hold themselves in almost a standing position on their hind legs.   The larvae live underground.  It is said that the female will climb from the ground to mate and then after a copulation of less than twenty seconds drop down again to re-enter the soil. [If the females are so rare, how does anyone know this?]  It is further claimed that the males do not attract the females  in any positive way.   Why then, one wonders, do the males  sit in such a strange  manner on the leaves, and why are they so brilliantly coloured?   Can there be any other reason than to attract the females?
It is classified with a subgroup of scarab beetles. . This species is found only in Southern France and Catalonia in Spain.

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