Thursday 28 June 2012

Tree sculptures and lesser stag beetles

In the last three weeks, I have been coming across Lesser Stag Beetles (Dorcus parallelipipedus) dead on the pavements in my street. June and July are peak emergence time for these dark, flattened beetles. Today we found 10 squished ones and a live one next to a chestnut tree stump, is this were they were coming from? I got the impression that the beetles might have been seeking shelter under the wheels of a car parked next to the stump, and they were inadvertently squashed every time the car moved. This tree stump used to be a tree sculpture (here for a photo, yes, the car behind is the beetle squasher!). Old trees that have got too big are partially felled in our neighborhood to avoid subsidence and then carved into statues. The dry dead wood soon becomes peppered with many tiny beetle holes, which are taken over by little wasps to nest, accompanied by their suit of parasitoids. The sculpture was taken down last year as it had started to rot and become unstable. The remaining stump was as soft as crumble. When I looked into it today, many large exit holes were visible on the surface. I dug a bit into the rotting wood with a stick and it didn't take long to find a Lesser Stag Beetle larvae. They have a large head, strong dark mandibles to chew the rotting wood and a c-shaped body curled underneath. The larva was very active, it turned round and quickly moved away hiding into the wood. Millipedes, woodlice and earthworms shared the dead wood with the beetle larva.
The collection of dead Lesser stag Beetles. The one on the bottom left-hand side is a large male with impressive jaws. There is huge variation in size amongst individuals.
A close up of the stump with exit holes.
An overview of the Chestnut tree stump
A side view of the young larva
Lesser Stag Beetle larvae take over two years to develop, and several stages may coexist in the same stump. Adults also may live several years, so it is a shame so many are dead, but this stump probably holds many tens of larvae and many adults have probably already dispersed successfully after emergence. 

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