Red Admiral hibernation

[Nick Bowles]

On Sat, 16 Jan 1999 16:34:24 +0100 (MET), =?ISO-8859-1?Q?Morten_Dewald_Dr=F8gem=FCller_Hansen?= <dd at imf.au.dk> wrote:

> Hi Leps-netters
> 
> Following the posting by Martin Honey, I would like > to emphasize that Red
> Admirals (Vanessa atalanta) and Painted Ladies > (Vanessa cardui) do not
> hibernate. They are inactive because of low > temperatures but as soon as
> temperatures rise, the butterflies will become > active. Hibernation shows a
> dramatic decline in metabolic activity which is not > the case for atalanta
> and cardui.
> 
> The Red Admiral and many other large Nymphalid > butterflies enter a
> reproductive diapause when autumn arrives. > Hibernation is a part of this
> reproductive diapause in P. c-album, N. antiopa, A. > urticae and I. io, but
> atalanta and cardui migrate south, escaping winter in > space rather than
> time.
> 
> kind regards
> Morten DD Hansen
> Dept. of Zoology
> University of Aarhus
> Denmark  
> 
>Quite possibly many butterflies do move south in autumn.  There is very little evidence for that from the UK. Numbers certainly fall off from the north but few people have been able to point to actual southward movement in the same way that northern movement is een in hte spring. Many of the latest/earliest sightings here are of Red Admiral (V. atalanta) and Painted Lady (C. cardui).
However, there is evidence in the UK that the metabolic activity is lowered to such a state that it is certainly hard for me to see the difference. Only one Painted Lady  has been 'proved' to survive from October in one year (1997) until April the following year (1998), though others are strongly suspected. (Some of our early sightings are probably migrants as those sen in several coastal areas on Jan 6-11 1999). But there are many examples of well watched Red Admiral surviving similar lengths of winter.  Larvae of Red Admiral have been found in virtually every stage of development and there is little doubt that some do manage to enter a diapause stage to pass the winter.  IN fact the most likely cause of the failure of over wintering larvae is the virtually disappearnace of stinging nettle food plants in hte frosts of winter.  In the few instances where they feed on Pellitory we expect that they fare better. 

So I would like to know what is the difference between lowering metabolic activity to the point where insects survive for months; and hibernation.  Is there really sufficient difference that the two conditions can be reliably distinguished?

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