MARCH
1992

 

 

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

 

 

 

 

03-12-92

Turn About is Fair Play

When it's time to dine, insects choose their favorite foods: tasty plant leaves, stems and roots; succulent plant sap; and delectable plant flowers and fruits.

Plants, however, are not eager to be devoured by insects. Many plants have spines and hairs, sticky substances and even bad tastes to thwart hungry mandibles. Yet in spite of their attempts to protect themselves, most plants become the victims of insects.

Still, there are a few plants that have turned the dining tables on insects. These plants, called insectivorous plants, trap insects and make a meal of them.

The best known of the insect-eating plants is the pitcher plant, a native of North America. Its leaves and petioles are modified to form hollow "pitchers." Glands on the inside of the pitchers secrete a substance that attracts insects. Insects trying to reach this substance fall into a liquid at the bottom of the pitcher and are digested by the plant.

The sundew plant has leaves with numerous sticky hairs. Insects that get trapped in the hairs are digested in a fluid secreted by the leaves.

Another insect-eating plant is aptly named, the Venus's-flytrap. This plant has leaves that end in two lobes. The lobes are bordered by a series of spines. The plant just sits around with the lobes expanded waiting for a meal to come by. When some unsuspecting fly wanders into the center of the expanded lobes, the lobes will spring shut like the jaws of a steel trap. The fly cannot escape this plant. It is doomed to be digested by a secretioin poured from glands on the surface of the leaf.

For these plants, eating insects is more than a sinister method of getting even. Insect meals provide insectivorous plans with nitrogen. Most plants that eat insects live in wet areas where nitrogen is limited in the soil, so they need to supplement their nutirient uptake.

It's ironic that for a few plants a tasty insect not only provides a fine meal, but also gives them gas -- nitrogen gas.

 

Writer: Tom Turpin
Editor: Elaine Lambert