This striking butterfly, Vanessa atalanta,
is a popular visitor to gardens. Until recently little was understood
about its behaviour and much still remains a mystery.
robust butterfly, its wings are adapted for prolonged flight over
land and sea. It is not a species which hibernates, but overwinters
in France and Spain, whilst further south still in North Africa
it can continue to breed throughout our winter months. In mild
winters, Red Admirals can sometimes be found overwintering in
the south and west of England. On cold days they rest, emerging
on warm sunny days to feed and drink - unless they can do so at
regular intervals they do not survive here.
spring, migration northwards takes place steadily, those arriving
in Britain (at any time between late March and late May) go on
to breed and produce the butterflies that are such a welcome sight
in August and September in our gardens. Curiously, little is known
about where our breeding Red Admirals mate - until recently there
was only one well documented sighting of a paired couple in Britain.
Do the immigrant butterflies mate further south or only at night?
mild winters have caused a spate of reports of Red Admirals over-wintering
in Britain (there were 24 reports from 16 counties on 1st January
2007 alone), especially but not exclusively in the south, and
quite a few sightings of mating pairs. These might not be typical
matings, however, as the low temperatures at that time of year
would inhibit flight and prevent them rising out of sight, perhaps
into tree tops, as they normally would. In Cumbria I recorded
my earliest ever Red Admiral on 1st March 2007, probably one that
had over-wintered as there was no evidence of any other influx.
are laid on the common nettle. When hatched the larva constructs
a 'tent' by drawing leaf edges together with silky threads. Four
moults take place before pupation, with the chrysalis protected
in another leaf tent. The adult butterfly emerges about two months
(depending on prevailing temperatures) after egg laying.
September and October the direction of migration reverses. What
triggers this is not known - shorter days, lower temperatures
or angle of sun are possible explanations. Now large numbers may
build up along the south coast of England, where they feed up
furiously for several days. Suddenly, usually when the wind veers
to the north, they are gone in a day or so crossing the Channel
overnight. Some stragglers, possibly because they have not been
able to feed up enough, are left behind and attempt to overwinter
here - usually without success. However, in recent years with
very mild winters, there have even been amazing cases where larval
development and pupation have been closely watched during the
some Red Admirals fly far enough south to continue breeding but
others overwinter in France and Spain without breeding is not
known. Are there two genetic strains of Red Admiral in Europe?
Red Admiral is a cosmopolitan species, being found in Central
and North America. Here it seems to follow a similar breeding
and migration pattern. It is a common species in New Zealand,
but it is unclear whether it was introduced here or not. One wonders
what the migration pattern is between the two islands - current
evidence suggests it is largely sedentary?