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02-24-05
Some Plants Get the Last Laugh
on Insects
That old crooner Frank Sinatra made the song "Love and Marriage" famous.
The lyrics suggest that love and marriage go together "like a horse and
carriage." Well, if Mother Nature had written that song, the line might
read, "Love and marriage go together like plants and insects." It doesn't
rhyme, but, as the song says, "You can't have one without the other!"
Yes, in the natural world, insects and plants are almost inseparable.
The insect and plant relationships mostly deal with food. Like in the
horse-and-carriage relationship, the horse, I believe, would suggest that
the benefits are decidedly one-sided. Mostly plants provide the food,
and the insects do the eating. There are more than 360,000 species of
insects that eat plants. This means that more than 25 percent of all named
organisms are plant-eating insects.
Among insects, nearly all of the Lepidoptera, the butterflies and moths,
and the Orthoptera, the grasshoppers, katydids and crickets, are plant
feeders. In fact, caterpillars and moths are the primary consumers of
plant tissue on the earth. These immature insects are real plant-eating
machines. There are also a lot of plant-eating beetles and true bugs.
Having all of these plant-chomping insects around means that many of
us look at insects as pests. After all, when we grow a plant as a crop
or in a lawn or garden, we are inclined to not want to share the foliage
with a hungry insect. Witness all of the insect-killing chemicals and
devices available at the local garden shop.
Plant feeding by insects not only antagonizes humans, it's not real good
for the plant either. After all, insects can defoliate plants entirely,
burrow into the stems or even cut the plants off at ground level. Consequently,
many plants have developed mechanisms to discourage insect feeding. Plants
have things, such as bad tastes or poisons, to ward off hungry insects.
Such as the case with love and marriage, you have to take the bad with
the good. In the plant-insect relationship, the good is that the plants
have developed a little arrangement where the insect helps with the process
of pollination. The astute reader might extend the analogy of love and
marriage here. But I'll stick to plants and insects.
Insects play an important role in carrying pollen from plant to plant.
The wind also does this. Some plants are self-pollinated, but many enlist
insects to do the job - sort of nature's UPS delivery animals. But insects
don't work for nothing. The plant has to pay a fee for pollen delivery.
But it is the barter system. The plant provides food for the insect in
the form of pollen or honey.
However, the promise of a handout is not enough. In addition, the plant
has a sophisticated advertising system to attract the insect - flowers.
These flowers are the beacons that attract the insects. When the insect
stops for the free food, the plant dusts their little bodies with pollen.
And some of you probably thought that flowers were there just for human
enjoyment! In reality, flowers exist for insects.
Like love and marriage, the insect-plant relationship sometimes takes
a turn for the worse. In some cases, plants turn the tables on insects
and start eating these six-legged creatures. The Venus' Fly Trap, a plant
found naturally in the costal areas of the Carolinas, is a well-known
insect-eater. It works by having two jaw-like sides of the trap, which
shut when an insect crawls inside. Then, the crushed insect is digested,
and the nutrients absorbed by the plant. The insect carcass is expelled
when the trap is reset.
The sundew is another carnivorous plant. This plant grows in bogs and
wetlands throughout the United States. Insects get trapped in sticky hairs
in leaf surfaces. Pitcher plants also trap insects in the bulbous pitcher-like
stems. In both the sundew and pitcher plant, the insect is digested.
There are more than 350 species of plants worldwide that consume insects.
Such plants would seem to be making up just a little for all of those
plants that get eaten by insects!
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