Re: pillbugs
From: Bill Shear <BILLS@hsc.edu>
Pillbugs are crustaceans, related to shrimp and lobsters. They are members
of the order Isopoda, about the only group of really diverse and successful
terrestrial crustaceans. So calling them "bugs" is technically
incorrect--they're not insects at all. I don't know if insecticides would
work on them.
In any part of the nation, about 10-12 species will be found in gardens.
Most if not all of these are of European origin. The nature of our native
isopod fauna will never be known, because the European immigrants wiped
them all out before they could be studied (not that anyone was in a hurry
to study them). A familiar story of aggressive aliens outcompeting native
forms.
Isopods eat dead or decaying plant matter, and except for a few tropical
forms, are not considered plant pests. But some people are disturbed by
their numbers, which can build up quickly in favorable conditions. In
fact, they might help by cleaning up rot and dead tissue around the bases
of iris plants. They need a good deal of humidity to survive, so one often
sees them in masses under rocks, etc., trying to stay damp. Most still
have gills, a few have weak tracheal "lungs." Not all species can roll up
for protection; actually only two common species can roll up completely.
Some sort of half-way roll up, and still others can't roll up at all.
I don't think any of our species have "color-coded" males and females.
Like all arthropods, they grow by molting, but unlike insects, isopods do
it by halves--the front half of the shell is molted first, then the back
half a few days later. The new shell is usually lighter in color (may look
pink) than the old shell, and the shells get darker as they age. Male
isopods search for half-molted females, then guard them until their molt is
complete, at which time they can mate. Another name for them is "sow-bug"
because the young develop and are carried in a pouch under the female's
body and bear a fancied resemblance to piglets suckling a sow.
Nothing to worry about.
Bill Shear
Department of Biology
Hampden-Sydney College
Hampden-Sydney VA 23943
(804)223-6172
FAX (804)223-6374
email<bills@hsc.edu>
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