Stag beetles have started to appear again in Flatford Wildlife Garden, so it seems like a good time to take a closer look at these fascinating insects.
Stag beetles live most of their long life cycle underground as a larva. The larvae spend between 3 and 7 years underground, munching on rotten wood and building up sufficient energy to emerge and mate when they reach adulthood. During this time, they shed their skin up to 5 times, growing steadily until they are large enough to pupate. Sadly declining woodland habitats have led to a reduction in rotten wood available to stag beetle larvae, meaning that the species is now considered to be globally threatened and is listed as a priority species in the UK Biodiversity Action Plan.
Pupation takes about six weeks and begins in the final autumn of the beetle's life cycle. The cocoons can be large, sometimes the size of an orange! The transformed adult leaves the pupa but remains underground until the following May or June when they emerge from the soil beneath logs and tree stumps. Adult males emerge first.
Adults live for just 4 weeks, with the soul purpose of mating. As the UK's largest species of beetle, they make a striking impression, especially the males with their large antler-like jaws. These jaws are used to battle against other males for access to females during breeding season, much like a male deer uses its antlers (hence the name of stag beetle). They also form part of the courtship ritual, with the male circling the female with its jaws raised and open to attract her attention.
Stag beetle Lucanus cervus, two adult males fighting
Ben Andrew (rspb-images.com)
The jaws of the male stag beetle may look fearsome, but are actually quite weak, making this beetle pretty harmless to humans. Males mate multiple times before dying, while females usually die in August once they've found some suitable decaying wood on which to lay their eggs.
Despite their amazing size, stag beetles can actually fly! Males will fly out to look for a mate at dusk on humid, thundery evenings between May and August, often at our face height, which can be a bit alarming! Female stag beetles are capable of flying but rarely do so. Instead they release pheromones to attract males to them.
So what can we do to help this protected species in our own gardens? As decaying wood is so important to them, the easiest way to help is to have trees and shrubs in your garden, and to leave any stumps of felled trees. The next best thing is to make a log pile, burying some bits or at least keeping the wood in contact with as much soil as possible. It also helps to cover your water butts and keep an eye out for the beetles in ponds - they can't swim but you can save them from drowning if you rescue them soon enough.
Flatford Wildlife Garden is open daily throughout the summer from 10:30-4:30; we look forward to seeing you there.