Researchers
observe a defense mechanism for caterpillars can attract unwanted attention
Date: December 17, 2018
Source: Ecological Society of America
When a
caterpillar disguises itself as a snake to ward off potential predators, it
should probably expect to be treated like one.
This is
exactly what happened in Costa Rica earlier this year, when researchers
witnessed a hummingbird defending its nest from what it interpreted to be a
snake, but was actually a larva of the moth Oxytenis modestia. The
encounter is described in a new paper published in the Ecological Society of
America's journal Ecology.
These
moths -- sometimes called the dead-leaf moth or the Costa Rica leaf moth -- resemble
flat dried leaves as adults. The caterpillars can inflate the top of their
heads to expose a pair of eyespots. When disturbed, they raise their head up
and move from side to side, increasing the snake-like appearance. In particular
they resemble a green parrot snake, known to prey on nesting birds.
The
attacking hummingbird's nest with eggs was about 10cm away from the caterpillar
in a small tree. When the researchers went to look for an assumed snake, they
instead found the caterpillar feeding on a leaf immediately above the nest.
"Hummingbirds
have a few stereotypical styles of flying: visiting flowers, preying on swarms
of tiny insects, chasing each other, and mating/territorial display
flights," says lead author James H. Marden, professor with the Department
of Biology at Pennsylvania State University. "Mobbing behavior directed
against a threat to their nest is much less common but distinct and easy to
recognize if you know their other flight behaviors... One can recognize this
from a distance and only notice the source of their agitation upon close
inspection."
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