Thursday 23 February 2012: mining engineers
The excavators of these little sand pits must surely be the mining engineers of the insect world.
With a son who is a mining engineer in the human world and a mere ten years experience of study and mine design, the millions of years of the ant lion scuttling around on this planet have perfected the intricacies of open mining a pit ...as a food scource.
Nicknamed 'devil-devil' in Aus, the larvae of the Myrmeleontidae family (think dragonflies, damselflies and lacewings ) traces a perfect circle in the sand.
Up to 8cm in diameter and 5 cm deep this little beastie excavates a conical pit to the 'critical angle of repose' (bear with me on this) which is all to do with the steepest angle the sand can maintain before it collapses.
The collapsing thing is what this hunter works on to catch a meal. As some poor unsuspecting ant, or spider come to that, wanders too close to the edge and loose sand it tumbles in.
Meanwhile, the ant lion is lurking in the bottom of the pit, concealed apart from protruding,snaffling pincers and as ant teeters on the edge the ant lion starts to undermine the slope by flicking up sand, collapsing the angle and hey presto....lunch.