I think it’s going to be a good year for stag beetles in East Dulwich. On May 16th there were three flying around in the evening, two males and a female. Then on the 29th I found the chap, pictured left, buzzing about as I was bringing in the washing off of the line. He’s small, but perfectly formed. At 35mm, excluding the antler jaws, he is way down below the usual size spectrum of 45-60mm. I’ve only ever seen one smaller, just over 27mm, found dead in a friend’s garden in Sydenham several years ago, although the books claim 20mm as the smallest on record. They can reach 70mm, and with the jaws on top of that, they can be monsters.

The seemingly extreme range in size is something to do with the stag beetle’s choice of larval food — rotten wood is very poor in nutrients. That’s why it takes 3–7 years of chewing away as a maggot before it has obtained enough protein nourishment to change into an adult. The problem with spending so much time in half-buried logs or mouldering tree stumps, is that the longer the maggot waits before turning into a beetle, the more likely it is to be disturbed by someone removing the timber, or to fall victim to predator, parasite or disease. The adult beetle may appear bold and imposing, but the larva, even a big one, is pale, soft and vulnerable.

There must be something of a nutritional gamble going on inside the grub’s metabolism — wait as long as possible to get as big and beefy as possible, or get out quick and hope that early emergence success offsets small size disadvantage.

I must make sure I send my record to the London Wildlife Trust’s stag beetle survey. Mr Beetle flew off into the dusk. Good luck to him.

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