DK Nymphalis antiopa update

[Runar Krogen]

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> Hi LEPS-netters
> 
> My first message dealing with the population crash of the Camberwell
> Beauty / Mourning Cloak (Nymphalis antiopa) in Denmark was a bit too
> pessimistic. The species HAS declined dramatically in Denmark due to our
> very cold summer but in the driest and most sunny areas in Denmark the
> species has persisted, though in low numbers.
> 
> I believe that the distribution of N. antiopa depends much more on dry,
> hot summers than it does on dry, cold winters. If there isn't enough
> sunshine, the larval and pupal development will be delayed and the
species
> won't be ready to overwinter...?
> 
> Any comments, please?
> 
> kind regards
> Morten DD Hansen
> Dept of Zoology
> Institute of Biological Sciences
> University of Aarhus
> DK-8000 Aarhus C 

Hello

Trondheim, Norway, which is situated close to the Norwegian Sea, has in
general  rather mild, wet winters and cool summers. Nymphalis antiopa is
only a migrant to this part of Norway. 

During early/mid nineties I did 3 overwintering experiments with the
species here in Trondheim. The specimens were collected in southern Norway
where it is a permanent breeder. They were placed in a wooden box outside
and therefore exposed to natural temperature and moisture. Included in
these experiments were also Inachis io, Polygonia c-album and Aglais
urticae. Only the last two species are native to Trondheim. 

Inachis io had the highest death-rate, then followed by Polygonia c-album
and Aglais urticae, both species at almost the same rate. To my surprise,
Nymphalis antiopa had the lowest death-rate. For example: In early August
1992 I collected 30 specimens and they were fed on plums for some time and
put outside in a shaded place around August 20. 28 of these survived the
winter and became active in early April 1993. This was even a mild winter!!

I agree with Morten DD Hansen and have done the same conclusions: Nymphalis
antiopa depends on a dry and warm summer, which we normally do not have
here in Trondheim, although there are exceptions. Dry and cold winters are
most probably not a necessity for the species. Therefore: The reason for
why it is not a native butterfly here in Trondheim is to cold and wet
summers in general.


best regards

Runar Krogen
Trondheim, Norway
rkrogen at online.no