(UK)Red Admiral hibernation

[Nick Bowles]

On Sun, 17 Jan 1999 16:33:02 +0100, Morten DD Hansen <biomddh at biology.aau.dk> wrote:

> Hi Morten,
Thanks for takingthe trouble to reply. I would like to go further into your reply and see if I can get a clearer idea of what's involved.
> 
You wrote 
> In Denmark we see substantial movements of Red > Admirals in fall, in some years more than 100.000 > individuals have been counted at one single spot per > day! From Finland there are reports (Jaakko Kullberg) > of 50.000 caught in traps at one single island in > autumn 1998.

while I accept that these probably are moving through the islands, do we KNOW that they are going south.  There are some similar descriptions from the UK though much smaller numbers are involved, mere hundreds. While it is assumed that they are going south, there are several people who think that they are just the effect of very succesful local breeding.  There disappearance the next day being down to dispersal in all directions.  I'm not saying this is correct; just asking.  I've seen film of radar signals produced by northward migrating insects in spring but I can't recall the same for the autumn return.  I'm asking do you know of any proof that they go south with the same intensity of purpose.
> 
you wrote
> Where are all the Peacocks and Small Tortoiseshells? > They are far more common in winter. Why don't they > fly when temperatures rise?


Answer they do; I have far more reports of Peacock and Tortoiseshell.  Since January 1st 99, Peacocks are most frequent (10), Red Admiral (4), Tortoiseshell (3), Painted Lady (3), and Brimstone G rhamni(2).  In 1998 the month of January produced Red Admiral (12), Peacocks  (10),  Tortoiseshell (9) Painted Lady (1) and Brimstone (4). These figures are undoubtedly biased as people are far more likely to report the 'unusual' Red Admiral and Painted Lady sightings, than Tortoiseshells.

>you wrote
> 
> If you subject well fed Peacocks and Red Admirals to > the same conditions (constant temperature at 4 > degrees C), Red Admirals die within 1 month, while > Peacocks have a survival rate of  more than 90% after > 180 days (Pullin 1987)! This might indeed indicate some > difference in metabolic activity.
> 
>I haven't seen this research.  can you give me a reference as it certainly supports your theory. Further your logic on why some stay here is so obvious that I wish I had thought of it myself. You wrote: 
> I think it's more probable that they have not had the > time to leave England in autmun and hence have to > overwinter. If the weather in autumn is poor, the lipid > reserves of the butterflies are rapidly depleted > (within 15-20 days). When the weather conditions > better, the butterfly has to choose between migration > or feeding. They feed.
> 
I wonder if this might also explain why some Red admiral are seen feeding on  a regular basis, whenever weather permits, while others remain largely immobile.  Those with the most lipids are able to spend longer without moving.

Finally ,for now, your comment on the larvae.  you wrote:> Diapause (which is neurohormonally mediated) has not > been reported in larvae of Red Admirals, but they may > survive low temperatures for a while.
> 
we have recorded larvae in November that haven't been observed to feed again until late March.  I accept your reasoning but it is a long time to pause - 16 weeks. 
> 


Conservation Officer  for  UTB\ Butterfly Conservation
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