Hypothesis on Commas and Currants
gochfeld at eohsi.rutgers.edu
Mon Oct 19 08:16:32 EDT 1998
I would appreciate comments as to whether the following makes
A century ago the Gray Comma (Polygonia progne) was never common in New
Jersey, but was apparently not rare within 50 miles of New York City
according to Beutenmuller's 1893 [yes 1898] compilation. John B. Smith
(1890-1900-1910) considered it occasionally common but local in northern
New Jersey. Comstock's 1940 work on the butterflies of New Jersey
considered it "not common", listing specimens from eight locations.
Today the Gray Comma is very rare in New Jersey, if it occurs at all,
with no records since the early 1980s. The Green Comma (Polygonia
faunus) was even less common than the Gray a century ago, and is also
"gone" from New Jersey if it was ever resident.
In our book on the Butterflies of New Jersey we speculated that
these might have been one of the victims of pesticide spraying. However,
we overlooked another important factor. The Gray Comma's primary hosts
in the east are Wild Gooseberry (Ribes rotundifolium and other species
of Ribes:gooseberries and currants). It rarely uses elms such and also
White Birch. The Green Commas also uses Gooseburry and Currants as well
as a few other hosts.
The Gooseberry and Currants happen to be the alternate hosts of
the White Pine Blister Rust, a fungus which devastated White Pines in
the early 20th century (one of our most important timber trees). As a
control effort the Federal Government sent workers through the
countryside (including peoples private yards and farms) to eradicate
these plants. The period was 1910's probably into 1930's. The intention
was total eradication of these wild plants (I presume the garden
varieties were to be spared). I haven't yet looked for reports on how
thorough these teams were, but this "surgical strike" on the habitat may
have had a hand in eliminating these two species. This would have been
compounded by the Dutch Elm Disease which wiped out most American Elms
in the 1950's and 1960's. Thereby denying Gray Commas any suitable host.
I would appreciate suggestions as to whether this makes sense.
Also have these commas declined elsewhere?
There was also a War on wild Barberries (Berberis) which are the
alternate host of Puccinia graminis, a cereal rust. The fact that White
Pine Blister Rust was brought under control antedated widespread use of
synthetic pesticides and is in stark contrast to ineffective eradication
of "insect pests" by chemicals. But that is another story.
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