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.
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| Wasp abdomen - still dangerous |
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| 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.
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| Hornet Hoverfly - Volucella zonaria |
