Thursday, August 20, 2009

Gatekeeper Pyronia tithonus

I am an amateur naturalist trying to learn something about everything alive in my garden.

Photo 1, taken on a sunny day in recent July shows a butterfly I found resting on a post in my garden. A few minutes with a butterfly guide and there's no mistaking it as The Gatekeeper (Pyronia tithonus).

My Gatekeeper was very obliging and gave me oodles of time to fetch my camera and take photo's. I might have thought nothing of this, but then I came across a nice online study by Christopher Young of 516 butterflies visiting a UK garden over three seasons. P.tithonus 'stuck around' for the longest of all. Whether this is simple coincidence or whether it points to a behavioural trait of the Gatekeeper I've no idea (an unrecognised butterfly habit awaiting study?).

A second common name for the Gatekeeper is the Hedge Brown. For some reason I prefer the first, though I can't imagine how it originated (anyone?).

The Gatekeeper in photo 1 is a male as confirmed by the dusky patches towards the centre of the forewings. In preparing this posting I came across a number of websites declaring that these are a source of pheromones. I haven't managed to locate an authoritative account to confirm this however (anyone?).

The Gatekeeper is a member of the Nymphalidae family of butterflies that includes some 25 UK resident species, amongst them my previously blogged Peacock . An obvious feature of both are the 'eye' spots. My quotation marks are carefully chosen having come across an interesting article by Stevens et.al. As I learnt in researching my Peacock butterfly posting, many studies have shown that the conspicuous wing spots of certain butterflies have a valuable effect as anti-predator devices, acting to startle small birds about the seize the insect. It has been widely assumed that the reason for this is that, to the birds, the wingspots resemble the eyes of larger predators (hawks, owls etc.). The paper by Stevens et.al. casts doubt on this however since their ingenious test experiments imply that the most effective patterns are not necessarily those that most closely resemble the eyes of predators.

Caterpillars of the Gatekeeper eat grasses. You can find an image of one here.

Sadly, that is as much as I have managed to learn about the Gatekeeper. I should like to have read a 2001 paper by Conradt et.al. that my web searching tuned up. From the abstract, I understand the authors' studies to have shown that P.tithonus can detect and orient itself by landmarks up to 150m away (an impressive distance sensing range for a small insect I'm sure you'll agree). Sadly however, like so much internet information about the natural world, the details are viewable only by making a payment to a private publishing house. Not something I, as am amateur, am inclined to do. Alas therefore, my curiosity and yours, dear reader, must go unsatisfied!

3 comments:

Maggie's Devon wildlife blog said...

Thanks for another informative post. We have gatekeepers around the house here too. 150m does indeed seem impressive!

Rachel said...

Send me an e-mail as I may have access to the full artical via the university library - rachel (dot) moutrie (at) googlemail (dot) com. very interesting post, we get gatekeepers in our garden as well and your photo has confirmed thats what they are.

Blackbird said...

Thank you for the informative post. Great blog!