El Nino and Butteflies

[Mark Walker]

>Any comments, observations, speculations?


An interesting topic, to be sure.  I would be very surprised if the severe
El Nino weather patterns of 1998 did not have a major impact on the
emergence and viability of overwintering Lep species, although I couldn't
even speculate on what that impact might be.  Surely in your (Daniel
Glaeske) part of the country, as in mine, winters are commonly characterized
by periodic ground-clearing thaws followed by extended periods of extreme
cold.  At least for the heartiest of species, I would presume that there
would be little dependency on the insulating effect of snow.

On the other hand, there is certainly a latitudinal band above which the
species count is dramatically reduced (all too familiar to me up here).
Perhaps yearly north-south fluctuations of southerly species are largely
dependant on ground temperature fluctuation and the insulating effect of
snow.  For this to be true, though, the mid-latitudes would have to be snow
covered for the majority of the winter season.

A corollary would be to consider what effect a solid frozen layer of topsoil
has in terms of protecting pupa (which are below the frost line) from the
elements of winter.  Without a good freeze, maybe the ground below actually
becomes too damp and cold.  It would be interesting to look at the
temperature gradient of the ground with and without a hard frost.

Here in Vermont, where the winters extend well into May, it is baffling to
me that any of the overwintering pupa which attach themselves to underbrush
can survive at all.  By April, much of the lowland is underwater, only to
freeze over again by another blast of arctic air.  Ice storms, while milder
than what we saw last month, commonly coat all plants with 1/2 inch of ice.
I know that Papilio polyxenes handles this with no apparent problem.
Amazing, to say the least.

Thanks for the diversion.

Mark Walker
Castleton, VT