(Click Beetles or "peeny wallies")

"Peeny wallies", also known as 'click beetles' are always a source of wonder to visitors at Windsor as they noisily zoom around with their bioluminescent "headlights" shining .

Click beetles are so called because they have a jumping mechanism composed of a prothoracic projection that fits into a socket on the middle part of the thorax, which when activated makes a clicking sound. When placed on its back or held in one's hand, a click beetle will flex its prothorax against the socket and catapult itself several inches into the air attempting to right itself and escape, making its namesake sound.

But most people's interest is more aroused by the two dorsal light organs, which resemble two automobile headlights (a reason why in Brazil these beetles are called 'Automobile bugs') and a single ventral organ visible from below and only when the beetle is on flight. Researchers suspect that this ventral organ is in fact used by the males as a mating signal to attract females, which are typically found on the ground with their dorsal lights on. Very interestingly, this ventral light is located in the rear part of the abdomen, which is hinged so that, in flight, the male can tip its abdomen upwards and display this extraordinarily bright light.

We know of one research project currently being undertaken by Sebastian Velez from the University of Notre Dame, who is looking at the evolutionary genetics of these incredible bioluminescent click beetles. His study concerns the evolution of polymorphism for light colour which is occurring in Jamaica. While the colour of the light organs of Caribbean click beetles has diverged (so that the Belize species has green dorsal and yellow ventral, Dominican Republic has green dorsal and ventral and Trinidad has green dorsal and yellow-orange ventral), Jamaican click beetles are the only organism known to be polymorphic (i.e., several phenotypes occur within the same population) for light organ colour. Here, the dorsal light may be green or yellow-green, while the ventral may be yellow-green, yellow or orange. The orange-light beetles are found in higher frequency at the eastern end of the island and seem to be spreading both in space and frequency towards the West. Sebastian is studying this distribution and the selection process which may be causing the alleles coding for the orange color to spread.


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