I recently asked Sarah White to write a blog about the most annoying organism found at Loch Garten. Although her article on Nimrod was well written and informative, it wasn't quite what I meant. She then rewrote this fascinating piece that will make you look at a certain creature in a whole new light...Enjoy!
Hello blog readers! Sadly, summer is marching on and our wonderful Ospreys are spending less and less time on the nest. I am writing this whilst sat down in the kiosk on an overcast but still morning here at beautiful Loch Garten. Weather conditions which unfortunately, in late summer, signify the added irritation of clouds (and clouds and clouds) of midges.
Indeed, this morning, the usually quite satisfying task of filling the bird feeders was transformed into what felt like a tortuous endurance challenge. A dense swarm of the little blighters had parked themselves directly over the stores of bird food. As I fled the scene, armed with a feeder full of sunflower seeds and shouting obscenities, I resolved to finally write the blog post I’ve been planning for a while, a concise essay entitled ‘The awesomeness of the Highland midge Culicoides impunctatus’. So... without further ado... grab a cuppa and a comfy seat and prepare to love the midge!
We shall start at the very beginning (it’s a very good place to start...). Midges belong to the insect order Diptera or ‘true flies’. These are flies that have altered hindwings that form balancing organs (or halteres) and includes horseflies, mosquitoes and blowflies among others. There are many species of biting midges and they are found right across the world having adapted to live in a number of hostile environments including at a height of 14,000 ft above sea level on the slope of Mount Everest. In Scotland we have 36 different species of biting midge which thrive under a variety of conditions and habitats, however the "biting" we experience only occurs in 4-5 species. The most voracious being Culicoides impunctatus or the Highland midge.
Lifecycle
One of the reasons midges are so successful in the highlands is because their lifecycles are so well adapted to the weather and conditions. As with most insects they have a number of egg and larval stages before they emerge as adults. These egg and larval stages only last a few days, before the midge spend up to 10 months as a small maggot-like larva. The optimal habitat for this larva is blanket bog and upland mires, a habitat readily available across the highlands. They require a constant supply of moisture and drying out can be problematic, therefore dry Springs can be a blessing. The larvae are predicted to be present in the soil at a ridiculously high density of up to 10 million larvae per acre and feed on nematodes, bacteria and fungi present in the soil, occasionally even turning cannibalistic!
The first adults fly at the end of May and are mostly male. They form smaller swarms, dancing to impress the females. The males do not feed on mammals, but live on decaying plant and vegetable matter, and are therefore not a pest for us humans. Females emerge and are ready to mate and then begin to lay eggs. In order to lay their eggs the females must first obtain a source of protein in order to develop the yolk, which will nourish the offspring. For many species of insects this means they must find an external source of protein. C. impuctatus are autogenous insects, which means the females have the ability to mature the first batch of eggs without having a protein meal as they can break down and use parts of their own wing muscles! After the first batch of eggs has been matured however, an external source of protein is required for subsequent egg batches. At this stage the females become fixated on locating a blood supply, normally from cattle and sheep, but occasionally from humans. This is when peak midge season truly starts! Once a pregnant female has found a good source of blood she lets off a pheromone which advertises the protein source to other pregnant females. Hence the saying ‘kill one midge and thousands arrive for its wake!’
When the females bite they use their well adapted mandibles and maxillae to cut the skin with a scissor-like action and then insert their tube-like mouthparts into the wound. Their saliva contains an anti-coagulant to prevent blood clotting and crucially the midge actually exploits the body’s reaction to a wound. When damage occurs the human body produces a histamine reaction to counter any infection but this has the effect of widening blood capillaries and increasing the blood flow. This gives the midge a crucial 3-4 minutes of good feeding time before the white blood cells arrive. The itchy spot left behind is in fact a result of the body’s own histamine reaction (therefore you could argue that the itchy bite is not the fault of the midge!).
Midges cannot operate when there is more than a breeze so windy days dramatically reduce midge activity. On days when the sun is shining the highland midge will also not be present in great numbers as low light levels are the trigger for activity, hence why they all appear to come out as the sun is setting, This also explains why shady spots (or forested areas) and overcast days are particularly bad for midges.
Role they play in the ecosystem
As with all living things midges play an important part in the wider highlands ecosystem. The larvae and eggs will provide and important food source for other soil dwelling creatures and the adults provide a source of food for our beloved swifts, swallows and bats. Most interestingly though is the effects midges have had on the use of the land in the highlands. In Russia biting insects have been shown to have an important part to play in protecting the fragile tundra habitat by ensuring grazing animals keep moving and do not overgraze in a single place. There is the potential for midges to offer a similar control in areas of the highlands. Furthermore there is no doubt that midges have played a significant part in limiting the impact and activities of humans in the highlands. Many activities from crofting and forestry to the tourism industry have been negatively affected by midge activity. It may be that midges have played a part in helping us ensure the landscape across the highlands remains one of the most sparsely populated areas of the UK.
Avoiding getting bitten
Despite finding midges fascinating if irritating, we still want you guys to visit us here at the Osprey centre so please don’t be put off! There are a number of things you can do to keep them at bay:
So there we have it! The fascinating world of the midge! I hope you now look at the midge with a new found admiration. However irritating it can be, such a well adapted and voracious organism deserves our respect and acknowledgement for the important role it plays in shaping the highland ecosystem. Most of the information in this post has come from a wonderful book entitled ‘Midges in Scotland’ by George Hendry, which I would recommend to anyone looking to find out more!
Thankfully our birds seem far better adapted to living with midges than we do! EJ and Odin are both busy fishing for themselves and the chicks. So far this morning EJ has bought in a whopping THREE fish to Odin’s pathetic one. The chicks are still clamouring to be fed by mum despite being well able to feed themselves at 12 weeks old. We have also, very excitingly been regularly seeing jays on the nest, hoovering up insects and pieces of fish. Jays are a species that weren’t seen in the forest up until 10 years ago and we are now regularly seeing 3 on the nest at a time, including a chick! Exciting stuff! There is still lots of activity on the feeders from juveniles including young woodpeckers, blue tits and green finches (another species which seems to be increasing in the forest). Finally the heather across the reserve is beginning to come into bloom carpeting the bog with a lovely purple haze.
Blooming marvellous: heather at Loch Garten
Devil's Tooth Fungus
Site Manager (People), RSPB Abernethy National Nature Reserve