Hello All,
The occurrence of a Large Yellow Underwing on the 3rd January at light is an
extremely interesting report by Jayne Herbert. Normally the adult Large Yellow
Underwing is found from June onwards till late September in a protracted
emergence period. Aestivating (dormant) females only develop eggs in their
ovaries when the length of day (in August) falls below a critical level - about
15 hours to give rise to autumn larvae. The caterpillar hibernates. The onset of
diapause (a kind of suspended animation which once triggered will not be
reversed until a specific set of favourable conditions prevail) would normally
be triggered by temperature or light levels but in the case of this species, the
caterpillar does not go into any real diapause as such but just slows to a halt
in very cold weather only to resume feeding when the weather gets a little
warmer. The whole process speeds up in the Spring and early summer to the point
of pupation. I have seen caterpillars of what I supposed is this species which
in their early instars are green in colour, in a semi torpid state on warm
winter days at the base of clumps of dandelion and other such low growing plants
presumably feeding when conditions suite, preferring to be almost underground
rather like a cutworm. In Cornwall with extremely mild, often wet winters, I can
easily imagine the caterpillar developing to maturity and pupating to produce
adults in April when local conditions suite. Perhaps this specimen found by
Jayne, developed in a particularly warm and sheltered aspect or could it just be
a migrant? Summer populations are known to be augmented by immigration but not
in the winter. A full study of the changing conditions and biology of many
temperate species and their early occurrence in recent years in response to
climate change is much needed and I welcome further comments from you all.
Best wishes for the New Year.
Phil Boggis.

---- Original Message -----
From: Jayne Herbert
To: Cornwall Moth Group (CMG)
Sent: Tuesday, January 03, 2006 3:10 PM
Subject: [Cornwall Moth Group] Large yellow Underwing


After a very long period of finding absolutely nothing in my trap, I had a
Large Yellow Underwing this morning.
The earliest I've ever had them before is April.
Is anyone else catching anything at the moment?


Cheers
Jayne


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