Tuesday, 8 January 2013

Winter moths

We have a few moths that only emerge once the frosts have arrived. At first glance, this seems to be a flawed plan, since there is little vegetation to support caterpillars and the low temperatures are a hindrance to cold-blooded species (and none of our butterflies have this 'alternative' lifestyle plan). But a bit of investigation reveals that these winter emerging species might actually have a couple of advantages. Firstly, there are no ichneumonids or tachinids around to parasitise them at this time of year. Secondly, there is much less competition for any limited food resources that do exist. Thirdly, the eggs stay inert for a while, so their caterpillars don't hatch until fresh leaves are available, and they pupate before the real competition for summer food arrives. (This early pupation also provides some limited protection from parasites and predators). Furthermore, male moths are generally guided to the female by smell, and the summer moths can travel great distances overnight as they search for a mate, but many (not all) of the winter emerging moths have flightless females that stay in one place after they hatch. This means that the males have much less hunting to do to find a mate, which is a bonus in cold weather. There are some summer-hatching species with flightless females, so it would be interesting to know which came first: the winter hatching or the flightless females. More research, I think.

Here are a couple of winter moths which I photographed in December:

I photographed this very fresh (the abdomen is clearly still pink) Pale Brindled Beauty on the 19th of December, although its normal peak season is in March. This tied in with my sightings of Bumblebees, Celandines, and Willow leaves and catkins all around the same time: all of those would be much more normal in March than December.

Pale Brindled Beauty
I have subsequently discovered that this is the earliest ever date (by one day!) in Ireland for Pale Brindled Beauty to be recorded.

I also saw the very handsome Mottled Umber on December 25th:

Mottled Umber
At first I thought that this was a new species for me, because I had certainly never seen the moth before, but my records show that I had photographed the caterpillar in 2006 (you can see it here). So it's a new adult moth, but not a new species for me.

Both of these moths feed on leaves of a wide range of trees when caterpillars. In each case, the photographs show males, because the females of both species are wingless.

For the last week or so, the wind has been mostly from the south, and I received reports that immigrant moths have been found in the south of the country. I didn't think that they would bother at this time of year: perhaps it's yet another sign of a mild winter to come.

4 comments:

Caroline Gill said...

The Mottled Umber is magnificent. I was under the impression that I had seen the last of the moths before spring, but I have had one or two at the window.

The Weaver of Grass said...

Thanks Stuart for the tip on Windows 7 - so many people say the same so shall certainly stick with it.

Gill said...

Beautiful, aren't they, in close-up? Not many moths here (there were more before Christmas I think). One or two gnat-like flies though - and several flowers out, e.g. dandelion, buttercaup, deadnettles, mouse-ear, but intriguingly neither snowdrops nor aconites which usually are out by now. Strange.

stuart dunlop said...

@Caroline I'm not sure of the exact number, but there are around a dozen moths that can be found at this time of year. Many are nocturnal, though.

@Weaver Glad to see you're around and hope you're well.

@Gill I'd say that Dandelions, Daisies, various cresses, Herb Robert, Red Deadnettle and Common Fumitory are now perpetually in flower around here. I saw one Snowdrop in bud today. Plenty of gnats and I also saw a Bluebottle today. I suppose if bees, flies and trees are confused about the season, then seasonal species might also be conversely confused.