Wednesday, 4 June 2014

Do moths need a break?

Rain has returned and the trap is enjoying a rest. So are the moths which I think may be welcome. I often wonder about the effect of shining the lamp night after night and I raised it with Marc Botham, one of the many experts on the Upper Thames Moths blog to which I also contribute (rather more pithily) from time to time.

He is the butterfly ecologist at the Centre for Hydrology and Ecology near Wallingford on the other side of Oxford and, like other scientists, he has not merely studied this issue but conducted impressively painstaking experiments. He has kindly allowed me to quote from an email which I found fascinating - and encouraging:

"I trap nightly and have had other moth-ers lambasting me saying that all I’m doing is recapturing the same moths and showing nothing therefore. To prove this theory wrong I laboriously decided one year to mark several hundred moths, mainly Heart and Darts, but a number of other species too. Each night I would mark all of those I caught and release them within literally 1m of the trap (not even the other end of the garden). Then the following morning I would record all those with marks on and mark all those without with a different number. By the end I had marked a lot of moths and with between 50 and 100 Heart and darts coming in each night I was recapturing no more than 3-5 marked individuals per night. Other species were more prone to recapture, but my over-riding opinion is that there is an extremely high turnover. I think Hawk-moths and the like might be a little more likely to be re-caught if released so close to the trap and often, even without marking, I see the same individuals, recognised by tears in wings etc. More of a concern to me is that we may be stopping the moths from getting on with their normal activities – I often get eggs laid in the trap from desperate females and I wonder if they keep getting recaught that they might never search for their host plants which sees a whole generation wiped out, but then the above suggests this might not necessarily be the case – but I am involved in projects at CEH looking at the negative effects of lighting on moth populations so perhaps I may have to eat my own words at some point."

Not always a super-hero

I hope not. But Marc goes on to suggest that a much greater hazard comes from birds, including chaffinches and robins which have learned how to get into a Robinson trap (no mean feat for a bird and it's only ever happened to me once, in Leeds). I take the greatest care I can to redistribute my moths at times and in places which make it unlikely that birds will hunt them out. But the robins here certainly view me as some sort of Jamie Oliver or Hugh Fearnley-Whittingstall in food provision terms. 

Meanwhile, I have got one moth to show today - and to ask about - thanks to one of my sisters who lives in London, spotted it on a wall and got this well-focussed picture with the help of one of our nieces. I found myself in the position of many readers of this sadly scale-deficient  blog when she asked for an ID: how big was it I wondered?

Using the terminology of those who got the bottom grade in physics-with-chemistry O level, I enquired: "Was it a little scrap or more like a small butterfly/" She replied in similar scientific terms: "Smaller than a small butterfly but bigger than a clothes moth."

From this I deduce that it was one of those nightmares for the ID detective, the pugs, and I'm prepared to make a guess on the basis of a final note from my sister: "To the naked eye, it had a slight green glow which is only partially evident in the pic."

This makes me opt, in spite of the absence of those dots in the official picture of the species, for the dark form of the Green Pug (see example of the normal one a few posts back) which has the rather sinister name of form anthrax.  Notorious as the name of a very nasty disease, the word 'anthrax' comes from a Late Latin adaption of the original Greek for 'carbuncle'. It seems a rather mean name for this melanistic (and hence formerly common in London) little insect.

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