Green army on the ground at Norfolk Wildlife Trust's reserves
- Credit: Nick Goodrum
Reserves officer at Norfolk Wildlife Trust, Robert Morgan gives the lowdown on one of his favourite insects
In the shimmering heat of late July I’m occasionally stopped by a visitor and informed that: "There’s not much about on your nature reserve."
At the very grave risk of offending my many birdwatching friends, the antagonist normally has an expensive set of binoculars around their neck. I always answer: "Have you tried looking down?"
In late summer most birds have finished raising their young, there is plenty of food and in the heat of midday they are very probably taking it easy somewhere out of the way. Insects, on the other hand, abound in number and variety, thriving in the heat and sunshine, the hotter it is the more active they often become.
Of course there are butterflies and dragonflies to draw our attention, but if you really look down you may find one of my favourite insects, the green tiger beetle.
This ferocious predator of bare dry ground and patchy vegetation belongs to a family of insects called Carabidae or ground beetles.
There are more than 350 species of ground beetle in the UK with five of them classified as ‘tigers’.
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The commonest and most likely encountered is the green tiger beetle. It is, as its name suggests, a metallic green colour with cream spots that are bordered with black.
They have huge eyes, strong sharp jaws and are constantly active.
Being fast moving hunters they feed on any small invertebrates that are unfortunate enough to get in their way.
They are competent flyers too, and where numerous, scores can be found taking off in front of a brisk walker’s feet; a bounding flight will see them land several yards in front.
Living in small colonies, the beetles’ eggs are laid in separate burrows in the ground, when the egg hatches the resulting larvae will remain in the burrow, widening it to fit as they grow.
Like their parents they have formidable mandibles, and their burrow acts like a pitfall trap.
They will wait for passing prey such as ants or spiders, in fact anything that’s living, and they can drag into their lair.
They also have a spine adaptation on their back that anchors them in and prevents them being dragged out.
If you walk up to a colony the vibrations will drive them down into their burrows, but remain quiet and still for a short while, you will no doubt see them slowly re-emerging.
As it is with nature, the green tiger beetle doesn’t have it all its own way.
The larvae are often parasitized by a solitary wasp which will paralyse it with a sting, then lay an egg next to the beetle larvae’s immobile body.
The wasp grub will have a ready supply of fresh meat and a safe burrow to live in. The adult and larvae are on the look out for this particular wasp and will kill it if they can, but the wasp’s smooth and slender body make it difficult for the green tiger beetle to hold on to it, a battle of wits and will that has been fought for tens of thousands of years.
Green tiger beetles can be relatively easy to find in the right place, with Norfolk Wildlife Trust reserves at Buxton Heath, Holme Dunes and the paths and flood bank around Hickling Broad and Marshes good places to look. And, of course, you never know what other fascinating creatures you may find when you spend time looking down.
Bring back the beetles!
The Wildlife Trusts and the Royal Horticultural Society have just launched a national ‘Bringing Back Beetles’ campaign. The two charities are calling on gardeners to create habitats for these important but often overlooked insects which are a vital part of every healthy garden.
They will munch on garden insects like aphids and snails, while acting as food for our larger garden visitors such as hedgehogs and birds. Unfortunately, beetle populations are threatened by things like pesticides, habitat loss and climate change - but you can help.
Providing a patch for beetles, including ladybirds and ground beetles, is a great way to encourage balance in the garden and boost biodiversity.
NWT has a free guide to download from its website about Bringing Back Beetles in your own garden, which has instructions for building your very own beetle bucket, beetle bank, or dead hedge.
For more information, see www.norfolkwildlifetrust.org.uk