Phoebis sennae

[Bob Barber]

Hi all,

Here in southern New Jersey, we have had huge numbers of Phoebis sennae
(Cloudless Sulphur) since the huge incursion in August.  They did seem to
decrease in overall numbers in early September, but large numbers could be
seen in the vicinity of the host plant (Partridge Pea).  Many of those
observed in the latter part of September had probably emerged locally,
since most were very fresh.  Many eggs, larvae, and chrysalids could be
found.  Not being familiar with life cycles, I was a little amazed that
they were going from caterpillar, through pupation, to emergence in 10
days.  On the weekend of September, 26-27, I still recorded their numbers
as "hundreds."  On  September 28 we had a good cold front come through,
that triggered a large southward Monarch, and dragonfly migration (several
species), and some P. sennae appeared to be moving with them.  Since this
front, much smaller numbers of P. sennae are being seen.  There has been no
cold weather to do them in, in fact it has been balmy for this time of
year.  It is my understanding that these incursions are one way only, and
any succeeding generations from the incursion don't go south again.  I
certainly can't document a southward movement, but I can't understand their
disappearance either.  Anybody have any thoughts?

Bob

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Bob Barber  bob at hsrl.rutgers.edu
Histology/Pathology
Institute of Marine and Coastal Sciences
Rutgers University
Haskin Shellfish Research Laboratory
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