is temp the limiting factor on range

Ron Gatrelle gatrelle at
Mon Sep 3 14:19:04 EDT 2001

(I am passing this along to carolina leps group as the subject matter will
be of interest to many of them.)

Charleston SC is the type locality of Phoebus sennae eubule (Cloudless
Sulphur). Is this based on a resident or dispersed population?  I have gone
back and forth for this for a long time. Having done no structured study on
this I have come to an opinion. All stages of eubule survive the mild
winter here just fine - it rarely snows here and seldom gets below freezing
(or far below) in the dead of winter. (Charleston is a great place.)

The problem is host plants. If we have a few days of really cold for us -
below 32 for a couple of nights and into mid 40's in the days - followed by
70s for two or three days one is apt to see eubule out on those warm days
all winter. In spring there are often many freshly emerged eubule that
obviously came from "overwintering" pupae. Then as early summer comes
around there is a big drop off. The weedy hosts are not up and subspecies
eubule "dies out" - except in warmer winters where more southern specimens
are now coming back into the area - so adults are seen but oviposition is
not occurring. There is quite possibly some secondary plant(s) that may be
used as host in early summer - not known to me though.

This is related to the temp factor on range as eubule is certainly able in
all stages (which the most?) to cope with cold. A good college research
project here. How far north are eubule found in winter? Which stage is the
most cold resistant? How many other southern leps may fit the same
scenario. We think they are limited by cold but actually "die out" due to
lack of host plant rather than "retreat south" due to drop in temps. ????

----- Original Message -----
From: "Michael Gochfeld" <gochfeld at EOHSI.RUTGERS.EDU>
To: "lepslist" <leps-l at>
Sent: Monday, September 03, 2001 7:20 AM
Subject: is temp the limiting factor on range

> With regard to the Queen of the Carolinas thread, Ron wrote about the
> "possibillity of overwintering in sheltered situations on the Carolina
> coast itself in the mildest years."
> I have made what I assume is the same assumption that winter temperature
> (or perhaps snow cover) limits the overwintering of southern species in
> the northern part of their range (or north of their normal range).
> The assumption follows that this accounts for the die off of species in
> the fall, and the re-invasion the following year (or at longer
> intervals) of southern species into (for example, NJ or New England).
> If this were the case, the overwintering stage of a species should be
> temperature sensitive with cold temp either killing outright or delaying
> development.
> But I wonder for how many of these northward invading species there is
> actual experimental evidence that cold in winter IS the proximate
> limiting factor.  We do see adult survival limited by the early or
> delayed arrival of winter (but that seems to be a different question).
> For example, My wife, Joanna Burger, showed experimentally that summer
> temperature influencing incubation and development (rather than winter
> temperature influencing adult survival) might impose the northern range
> limit on a snake species.
> Or, how often do we see survival in the north  (and early spring
> emergence) of such species after truly warm (snowless) winters (i.e.
> after 1999-2000 or 1998-1999).
> Mike Gochfeld
>  ------------------------------------------------------------
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