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Wednesday, 14 September 2011

Small but silver

More unsettled weather, though the winds have died down. So only a few moths, and most of them predictable. This one interested me, however: it's only a Silver Y (I'm 90 percent sure, although I get muddled by the rather similar Golden Y and Beautiful Golden Y), but it seemed unusually small.


Since you may not be familiar with the size of a Sainsbury's 'Taste the Difference' eggbox, and since the moth was peacefully sleeping, I took it inside and lined it up with Penny's old printer's ruler, from her days as chief sub-editor of Cosmopolitan. I could give you the measurement in points, but here it is in millimetres: 15.


This suggests a Silver Y, whose forewing length is 13-21mm according to Waring, Townend and Lewington whereas the other two start at 17mm. Aren't I getting scientifc in my old age? Note, though, the different effects of light (a) outside and (b) in our kitchen. It reminds me of a mirror I once had in a hotel in San Francisco which showed how you looked in daylight, bright office light and subdued restaurant light. As I recall, the last was the most forgiving. Update: see very helpful comments which suggests that this is indeed a Silver Y, a small version due to starvation as a caterpillar known as 'gammina'.
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3 comments:

  1. Nick Tanner14 September 2011 at 21:21

    Martin

    your Silver Y could be of the form "gammina" which is thought to be smaller than normal examples as a result of starvation as a larva; also, is it just me or are Silver Ys a little scarce this year?

    regards Nick

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  2. Stewart14 September 2011 at 22:30

    Hi Martin, Silver Y is quite scarce this year. In 2010 I caught up to 50 in a session, but this year I have not exceeded 4. I catch a few of teh small form gammina. Much smaller and greyer than the nominate form. If you check the 'Y' on silver Y it is solid, on the other two it is generally broken into a dot and a V mark. It is a bit late for BGY and PGY now though...

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  3. MartinWainwright14 September 2011 at 22:54

    Thanks very much, both. I am sure that it is one of those gamminas. It struck me immediately how small it was and I was a bit disappointed that Penny's ruler put the forewing at 15cm when it looked less.

    I wonder if the French word gamin meaning urchin, waif or kid comes from the same root - in the moth's case presumably a diminutive of gamma, as in the Greek letter which looks Y-like, lower-case?

    All warm wishes and thanks again. Commentors such as yourselves are the rock on which I stand...

    Martin

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