Butterflies are one of
life’s pleasures. They are beautiful, varied and ephemeral. The way they come
from some less than cuddly caterpillar creature is nothing short of amazing.
Rearranging all those body parts whilst they are pupating is a feat of juggling
with your eyes shut that leaves me in awe.
Now some butterflies live short lives, some
hibernate over the winter when there is no nectar to sup, but some are
adventurers. The monarch flying from the upper parts of the United States down
to the Amazon to enjoy the tropical beneficence and keep out of the snows, is
well documented. It is sad that habitat loss from one end to the other of its
route is putting it under stress.
Europe also has its migrants,
and the Painted Lady, Vanessa cardui,
is one that winters in Africa. The very large group of Stefanescu et al have published their study of this
gem in the current journal of Ecography (1). This was no small effort. It
included radar monitoring as well as ground based studies and brought in
citizen crowd sourcing science work to follow the migratory progress.
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| Painted Lady Alvesgaspar, Creative Commons |
The Grand Migration, (and
it is fair to call it such,) takes six generations to complete the cycle. It
broods continuously as it goes and the numbers can be huge – many millions on
the wing. The populations steadily advance Northwards during the spring until,
finally as Autumn approaches, they have to head South to the equator, thousands
of kilometer away.
Those little fragile wings
catch the wind and the butterflies take advantage and fly high to get the
fastest drift. They can be found flying their hearts out over a kilometer up in
the sky, should one take the time to look. The trip from the heart of Africa to
the fringes of the Arctic Circle and back means that they clock up ~14,000 km at
speeds up to 50 km/h.
The number of immigrant Painted
Ladies to the UK in 2009 was ~11M and they prospered so that ~26M emigrated in
the Autumn that year (2).
- http://onlinelibrary.wiley.com/doi/10.1111/j.1600-0587.2012.07738.x/abstract
- http://www.bbc.co.uk/nature/19991550
