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

August 2018

In the June Nature Notes, I mentioned seeing a barn owl flying over the field at the back. 

Not the barn owl mentioned in the text, just the best shot of one that I've got

Well we have seen it several times since then, each time carrying prey and it appears to be nesting in a dead tree at the back of one of the houses on Pett Road, possibly Wetherdene?  A few days ago as we were sat by the pond sipping an aperitif and watching the sunset, we were alerted by a lot of screeching and flapping.  It all happened very quickly but basically, a kestrel was mobbing the barn owl which eventually dropped the prey which the kestrel followed down onto the field.  The barn owl then flew back towards Pannel Valley.  Only a few minutes later, the barn owl was back again with more prey.  I suppose that it is possible that the returning barn owl was the other parent that had already caught another vole while the first was being mobbed as male and female are almost identical.  (The male is slightly paler apparently.)  Another possibility is that the mobbed barn owl deliberately dropped the prey to avoid being followed back to the nest by the kestrel. 

Mobbing of owls by kestrels is well documented on the internet and many people have managed to take photographs or videos.  Sadly the only thing I had to hand at the time was a glass, but even if I’d had my camera with a long lens already switched on I doubt that I would have got even a blurry photo, it all happened so fast.

 ‘Our’ swallows have successfully fledged four chicks this year and it was delightful to watch them sitting on one of the beams in the carport waiting to be fed.  That only happened for a few days as they find their wings and fly increasingly longer distances and eventually come back only to roost.  We’ve not seen the youngsters for a while now, but the parents are busy preparing for the next brood.  The house martins seemed to be late nesting this year.  There is a nest at the front of the house as well as one at the back.  Both nests are from previous years, but that is not really surprising considering the shortage of mud at the moment.  The nesting habits of the martins are a bit mysterious.  Each year we see a lot of activity when the martins arrive back from Africa as they investigate each nest, but then it is often a month or more before they occupy the nest.  The nest at the front has three chicks, but the parents are still sitting on the nest at the back with no sign of hatchlings as I write this.

A while ago, I wrote about flying spiders – the process where freshly hatched spiders eject silk to catch the wind and help them to disperse – a behaviour called ballooning.  Recent research however, has shown that this is not the full story.  Some researchers at Bristol University suspected that naturally occurring electrostatic charges played a part (the sort that build up and cause thunderstorms).  They put spiders in a box inside a Faraday’s cage.  The Faraday’s cage shields the apparatus from natural electrostatic charges and allows the researchers to control the field inside the box precisely.  They found that increasing the electrostatic field encouraged the spiders to balloon and that once airborne they could raise or lower the spiders by changing the field strength.  A biologist also examined tiny hairs on the legs of the spiders that reacted to the field and gave the spiders the means of detecting the field.  Clever stuff indeed!