Last night I found a Dark Giant Horsefly (Tabanus sudeticus) on the wall of the Devon and Exeter Squash Club. This is the largest horsefly in Britain and they don’t get any bigger anywhere else in the world including the tropics.
The body is 24mm long – the orange base to the antennae and dark markings on the abdomen are diagnostic. This is a female – they have gaps between their eyes. In the males their eyes touch.
I’m not sure what it was doing at the Squash Club, I’ve normally seen this species in wild remote places like the Highlands, the Lake District and Dartmoor. I wonder whether it had been affected by yesterday’s heavy rain and took shelter before setting off again in search of cattle and horses.
Here is a photograph of the same species – one I took on Dartmoor a few years ago with a pound coin for scale
This is the same individual showing its mouthparts – it is only the females that bite – little reassurance though as this is a female!
This is the national distribution of the Dark Giant Horsefly – not very common
For me the best bit about this fabulous hot and sunny weather is that it really brings out the insects! A couple of days ago I was in the wet meadows at Parke and saw this very large horsefly quartering the grassland. I managed to net the insect first time and successfully transferred it to a pot so I could inspect it more closely. I brought it back to the office and put it in the fridge for half an hour to calm it down. I was then able to take the following photographs.
As you can see it is a very large horsefly – yes that is a £2 coin which gives you an indication of its size.
This species is Tabanus sudeticus or the Dark Giant Horsefly – this is a female (you can tell the sex of the adults by looking at the gap between the eyes: gap = female and no gap = male. This individual is 25mm long! This is as large as horseflies get anywhere in the world including the tropics. The orange antennae and black bands on the abdomen are diagnostic of this species.
Here is a frontal view – the long ‘dagger’ under the antennae are the mouth parts. Horseflies as we all know suck blood from animals such as cattle and horses. It should be noted that it is only the females that drink blood and they only do so when they are preparing to lay their eggs. The rest of the time they feed on nectar from flowers.
Here is the UK distribution of the Dark Giant Horsefly – it has a limited distribution and is much rarer than it once was.
Last year I was in Scotland and the Lake District and on both occasions I found Dark Giant Horseflies – here are some photos I took from the National Trust’s property Aira Force.
In case you are thinking of having nightmares – these giant horseflies don’t like human blood and instead specialise on horses and cattle. Other horseflies – particularly the clegs and the gadfly do bite humans but are much smaller – nevertheless the bites are painful and irritating so watch out! Clegs have skinny red eyes and gadflies have shiny green eyes in case you are wondering ….
You will, I am sure also be pleased to hear I released the animal back into the wilds of Parke after I had finished photographing it – maybe you will come across it too.
During my trip to the Scottish Highlands and the Lake District I managed to take some photos of some insects I have never seen before.
This is the dark giant horsefly Tabanus sudeticus – a female nearly an inch long! Fortunately it prefers the blood of cattle and horses to people. Saw one individual at Castle Urquart on Loch Ness and this one was taken on the National Trust property Aira Falls beside Ullswater.
Substantially bigger than the horseflies (normally Tabanus bromius and autumnalis) that I have seen before
It has been recorded in Devon and on Dartmoor but I have never seen it.
You might also be interested in Matthew Oates’ article on biting flies – see here!
Second up is a beetle – one of the chafers Trichius fasciatus – known also as the bee beetle or bee chafer. Its one of those animals you see in the books because it is so spectacular – finally I have seen one in the wild. Saw it at Loch Achilty, north west of Inverness in the Highlands. A Forestry Commission site.
A really striking beetle with long brown hairs on the thorax.
Only really recorded in the UK in the Highlands and Wales.
Finally another fly and another big species – its called Tachina grossa – or the yellow faced fly. It is very striking and large – nearly 3/4 inch long.
The female lays here eggs on the larvae of other insect larvae – often an oak eggar moth – which the hatched maggots then devour and kill!
A more cosmopolitan species – again on Devon and Dartmoor – one to look out for – unmistakable.