HO HO WHAT?
cherubini at mindspring.com
Thu Dec 13 20:42:24 EST 2001
> The point I want to make is if we want to find out more about how Monarchs
> get here, we don't need people releasing them in arbitrary places to muddy
> the waters.
Actually determining the natal source of the monarchs seen in the British
Isles each fall is rather easy. Just catch a few butterflies and determine the
cardiac glycosides they contain. If they contain the cardiac glycosides of
Asclepias syriaca milkweed it will prove they originated in the northerrn
USA or southern Canada.If they contain the cardiac glycosides of Asclepias
currassavica, it will suggest they originated in southern Europe or the
There are a three fundamental reasons why monarchs could not possibly
fly across the Atlantic on their own:
I. Monarch butterflies (like probably all butterflies) cannot maintain sustained
flight at night (except in urban areas near lights). 45 minutes after sunset,
monarchs will plummet to the earth if tossed into the air even on a hot full
2. Monarchs cannot rest on the surface of water more than a half
hour without becoming waterlogged.
3. Monarchs cannot maintain sustained flight in overcast
weather below 50 degrees F (10 degrees C) or below about
32 degrees F (O degrees C) in sunny weather, This rules
out any chance they could be carried on the jet stream to Europe.
Also, temperatures below about 24 degrees F are fatal to monarchs.
By contrast it is easy to imagine how Monarchs could cross the
Atlantic assisted by ships. Monarchs that fly out or are blown out
over the Atlantic coast of the USA, could land on ships and then leave
as they approached the British Isles a week later.
Bottom line is that releases of captive reared monarchs at events
in England/Scotland/Ireland will not substantially interfere with the
ability of scientists to determine the origin of wild monarchs that
usually appear in these countries each fall .
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