Nature Bulletin No. 597-A March 27, 1976
Forest Preserve District of Cook County
George W. Dunne, President
Roland F. Eisenbeis, Supt. of Conservation
Plants, generally, are eaten by insects or furnish other food for them.
But there are a few families of strange plants that, instead, "eat" insects
and other small animals. About 500 species are distributed over the
world, from the arctic to the tropics. Most of them have peculiar leaves
that not only attract insects but are equipped to trap and kill their
victims. Even more remarkable is the fact that some have glands which
secrete a digestive juice that softens and decomposes the animal until it
is absorbed by the plant in much the same way as your stomach digests
All of the carnivorous plants are small and, although occasionally a
dragonfly or a tiny frog may be trapped, the victims are usually ants,
flies, gnats, beetles, larvae, worms and small crustaceans. In North
America most of them grow in tamarack bogs, cranberry bogs, muskeg
bogs covered with sphagnum moss, and in swampy places, where the
brown water is acid and deficient in nitrogen. Their feeble roots serve
to supply them with water but most of their food seems to be obtained
from the animal matter they absorb.
The Bladderworts, however, are aquatic plants with long sinuous stems
and masses of fernlike leaves submerged in shallow ponds and swamps.
Along the stems there are numerous oval "bladders" each having a
small opening, surrounded by stiff bristles, with a delicate trap door
inside. If a larva, pursued by a minnow, darts into a bladder he cannot
get out. His body is absorbed by a great number of digestive cells that
line the cavity. Several kinds of bladderworts are known to live in
ponds of the Chicago region.
The Butterworts occur on wet rocks and gravelly places. These plants
have rosettes of long narrow leaves, each peppered with tiny glands --
about 25,000 per square centimeter -- that pour out a sticky "butter" and
digestive fluid when an insect alights upon them.
In the quaking tamarack bogs of northern Illinois and northern Indiana
we find a species of the Pitcher Plants. It has a clump of hollow tubular
leaves that look like pitchers with flaring mouths. They have red veins
and are mottled with green and brownish purple. The flowers, on stout
stalks, have five sepals, five petals, and are purplish red. The pitchers
are usually full of rainwater and drowned insects that were attracted to a
honey-like nectar secreted by glands on the lip. The inside of the leaf is
thickly lined with slick sharp spines that point downward. An insect
slides down into the water and cannot escape. His decomposed remains
are absorbed by cells on the pitcher wall.
The Sundews are another family of carnivorous plants that live in bogs
and there are two kinds found in the Chicago region. The sundew is a
small plant with a whorl of tiny round or spoon-shaped leaves on long
stalks that lie flat on the soil surface. The leaves have a glistening
appearance because of the hundreds of hairs on its surface, each hair
ending with a gland that exudes a sticky fluid. A gnat or a fly, attracted
by this "nectar, " is stuck there. The more he struggles, the more fluid is
secreted by the glands. At the same time -- and this is what Charles
Darwin considered one of the most incredible and wonderful things in
the plant kingdom -- all of the other hairs on the leaf bend inward and
surround the insect until he is suffocated. Then a digestive juice is
secreted and his remains are absorbed.
Most remarkable is the Venus ' Fly Trap, a sundew of the Carolinas,
whose sensitive bristled leaves close like traps to catch and "eat"
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