October 2018

You may remember that last month I wrote about hornets feeding on wasps.  I suspected that they leave the wasps’ abdomen because there is more protein in the thorax where the leg and wing muscles are located.  On a recent visit to Belgium with the short-haired bumblebee project, we met up with some Dutch and Belgian entomologists.  I was talking to one of the Dutch entomologists about the hornet and he confirmed that they only take the thorax for its protein content.  He also said that they don’t eat the thorax, but rather they mash it up into a manageable meatball and carry it back to their nest to feed the growing larvae.  Like their more useful cousins, the honey-bees, they make a bee-line for the nest.  Apparently, Holland has been dealing with the westward spread of the Asian hornet for a while now and they use this ‘bee-line’ habit to locate their nests.  All they need to do is to find a hornet and when it flies off with its meatball, plot its direction on a map.  When you have watched and mapped two or three hornets in this way, where the lines intersect shows you where to look for the nest, which can then be destroyed.  This may well be useful knowledge since as recently as the 11^th of September, Asian hornets have been spotted in Cornwall and East Yorkshire.

Great Green Bush-cricket - female

Another group of insects that we saw plenty of in Belgium were bush-crickets.  This is a striking group of insects and they are remarkable for the length of their antennae which can be many times longer than the rest of the insect.  We saw the great green bush-cricket, which as its name suggests is big and green.  The body can be up to 40mm long, and with an ovipositor another 20mm and antennae three times longer than its body, it looks a formidable insect.  I first came across one of them at Dungeness and my first reaction was one of disbelief.  It was bending the vegetation that it was crawling across.  Though large, they are well camouflaged in green vegetation and can move fairly quickly.  You are more likely to hear them before you see them as they have the loudest stridulation (chirping!) of any of our grasshoppers or crickets. 

Great Green Bush-cricket - male - showing just how big they are

We also found one species of bush-cricket that you are less likely to find around here - the sickle-bearing bush-cricket.  These were spotted in Hastings Country Park a couple of years ago, but have since disappeared again.  However, like many insects, global warming is inducing them to march northwards, and there have been other sightings around the country so if you see a bush-cricket with a sickle-shaped ovipositor, then take a photo – it may be a sickle-bearing bush-cricket – and the people who monitor such things want to know about it.

Sickle-bearing Bush-cricket - on my hand

I recently found one of my favourite bush-crickets – a speckled bush-cricket, on some red-leaved kale that we are growing.  Being bright green, it stood out well on the dull red of the kale.  With its long-legged awkward gait and its slightly goofy face, anybody would find it endearing, wouldn’t they?

Speckled Bush-cricket

Dave Clarke has recently had a small infestation of solitary bees in his garden.  They are probably ivy bees, another species on the march northwards (first seen in the UK in 2001).  I say probably, because there are two other very similar species – the sea aster bee and the heather bee.  (Dave's bees have since been confirmed as Ivy Bees.)  They are all called plasterer bees because of their habit of lining the cells that they dig in soft ground with a smooth cellulose substance.  You’ll have noticed that each of these bees is named after the plant that it prefers to feed on.  In Belgium one of the Belgian entomologists caught and identified a solitary bee from the fact that it was feeding on purple loosestrife, (which incidentally has green pollen).  It was one of the blunt-horn bees (Melitta nigricans) that we don’t get in the UK – yet!

Ivy Bee - Colletes hederae

September 2018

Underneath our apple tree are a large number of windfalls varying in state from eatable to completely rotten.  One reason (excuse?) for leaving them there is that it feeds the wildlife.  One of the main species to feed on the apples are wasps, but I was delighted recently to see a hornet cruising around the windfalls.  I was delighted because though they may be fearsome to some, to me they are a magnificent insect.  I have seen hornets feeding on the apples in the past, but this one had a different purpose in mind.  It flew towards an apple on which a wasp was already feeding.  There followed a surprisingly lengthy scrap between the two insects, but the outcome was never in doubt and by the time I got back with my camera, only the abdomen of the wasp remained.  Not sure whether there was any life left in it, I carefully nudged it onto a handy leaf and carried it out of the shade of the tree to get a better look.  I was wise to be so careful because within a minute or two, the abdomen suddenly started to try and sting anything within reach.  Clearly the hornet had stung the wasp to subdue it but the effect had gradually worn off.  A careful examination of the grass under the tree revealed several more stray wasp abdomens which suggests that wasps are a large part of the hornet’s diet.  I am guessing that it takes the head and thorax because there is more protein in the thorax due to the leg and wing muscles being in there.  

Wasp abdomen - still dangerous

European Hornet Vespa crabro about to behead a hoverfly 

Apparently a hornet sting is no more painful than a wasp or bee sting, each rated at level 2 on the Schmitt pain index, and each lasting around 10 minutes.  The pain index was compiled by the American entomologist Dr. Justin Schmidt, who wanted to know if social insects had evolved better defences than solitary insects because of their greater investment in the colony.  He allowed himself to be stung by more than 80 different species in order to compile the index.

On a similar note, we thought we had seen several hornets feeding on ivy flowers when we visited Kew Gardens recently.  Closer examination showed that they were in fact Hornet Hoverflies.  This insect also goes by the catchy title – Volucella zonaria.  It is a very convincing mimic and Britain’s largest hoverfly and is an example of what is called Batesian mimicry where a harmless species evolves to look like a much more dangerous species to avoid being eaten by predators.  This type of mimicry is named after a Victorian entomologist Henry Bates who first described the phenomenon.  He was a contemporary of Charles Darwin, and travelled to South America in 1848 with Alfred Russel Wallace who came up with the theory of evolution at around the same time as Charles Darwin.  Wallace returned from the Amazon four years later, but Bates stayed and studied mostly the insect life there for another 7 years, sending back thousands of specimens, many of which were new to science.  His collection survived the crossing back to Britain and in that he was more fortunate than Wallace, whose collection was destroyed by fire in a shipwreck on the journey back.  Bates wrote a very interesting book about his experiences – The Naturalist on the River Amazons – which is a classic of nature travel writing.  The hornet hoverfly also uses its mimicry in another way – to escape detection when it lays its eggs in the nests of hornets, wasps and bees where the larvae eat detritus around the nest.  A dangerous strategy indeed.

Hornet Hoverfly - Volucella zonaria