Caterpillar Defense: 'Freeze and Drop'
Researchers at the University of Würzburg in Germany discovered that
the beet armyworm, an infamous crop pest, displays the same defensive
behavior toward bees as it does toward wasps. In fact, the mere
presence of bees deters armyworms from munching leaves.
Armyworms, like many caterpillars, have sensory hairs near their heads
that detect air vibrations stirred by wasps' wings. When a wasp
approaches, an alerted caterpillar freezes and drops off the plant.
Thus, depending on the wasp species, it avoids being eaten or receiving
an injection of wasp eggs into its body.
Aware that bees' wingbeat frequency is similar to wasps', Jürgen Tautz
and Michael Rostás studied the behavior of beet armyworms inside tents
containing crop plants as well as bee feeders filled with sugar water.
Bees could access only half the tents, and the researchers found that
the caterpillars there ate 60 to 70 percent less leaf area than in the
"silent" tents. Energy wasted by dropping in response to a harmless bee
is apparently well spent to avoid the possibility of becoming a wasp
lunch or nursery.
As for the plants, they were the unmistakable winners. Conceivably,
interspersing insect-pollinated plants with crops could generate some
positive buzz in pest control.
The research was detailed in the journal Current Biology.











