Cabbage Butterfly defensive hairs.

Michael Gochfeld gochfeld at
Sat Nov 9 21:02:10 EST 2002

I just saw this Science News version of an interesting paper. from  of
May 11, 2002; Vol. 161, No. 19 . I thought I'd pass it on.
Pieris rapae and both species of Colias were flying today in Somerset,
NJ  when the air temp reached 64F.


No Tickling: Common caterpillars deploy defensive hair
Caterpillars of the European cabbage butterfly, which has invaded most
of North America, turn out to bristle with a kind of
defense system that scientists have not documented before.
 Picture online is POOR!!!!!!
YUK. Repellant droplets on hairs of the European cabbage butterfly
caterpillar send an ant into a cleaning frenzy (inset).
The caterpillars sprout hairs that carry droplets of a novel predator
repellent derived from a fatty acid, says Thomas
Eisner of Cornell University. Ants tend to avoid the caterpillars or
spend an unusual amount of time cleaning themselves
after contact, Eisner and his colleagues report in an upcoming issue of
the Proceedings of the National Academy of
"Here's something new about a species that's dirt-common," marvels
entomologist May Berenbaum of the University of Illinois
at Urbana-Champaign. Eisner's team named the oddball repellents
mayolenes after her. A footnote in the paper clarifies that
this is an honor.
The repellent-dotted species, Pieris rapae, hitchhiked to Canada in 1860
from its native Eurasia and North Africa. The
adult butterfly's chalky wings, with a dark spot or two, have become a
familiar sight coast to coast in the United States.
The repellent's defensive powers could easily have sped the species'
proliferation, Eisner says.
Soft and slow, caterpillars often turn to chemical warfare, he explains.
For example, some carry poisons that their fathers
transferred to their mothers along with sperm. Other caterpillars, when
attacked, regurgitate the remains of noxious
Researchers had previously documented defensive glandular hairs in
beetle pupae, and entomologists have speculated that the
little droplets atop the hairs of the cabbage butterfly caterpillars
might also offer some kind of protection. Eisner says
he knows of no previous attempts to test the idea.
In one behavioral experiment, his team confined a predator, an ant
species from the Northeast, with a European cabbage
butterfly caterpillar or a mealworm of similar size. The ants probed the
caterpillars much less often than they poked at
mealworms. In another experiment, the scientists washed the caterpillars
with solvent and then offered them to the ant. The
deterrent effect had disappeared.
To look into the chemistry behind the deterrence, the researchers
collected droplets from hundreds of caterpillars. The
deterrent chemicals fell apart easily when exposed to heat and acids, so
the team developed novel techniques. The
researchers learned that mayolenes are derived from a common fatty
substance, linolenic acid. However, the final compounds
more closely resembles substances produced in plants' injury responses
than in other caterpillar defenses, say the
Eisner says that he himself can't sniff anything repellant in the
mayolenes, much to Berenbaum's relief. "If they're named
after me, I sincerely hope they don't smell bad," she says.

Smedley, S.R., . . . and T. Eisner. 2002. Mayolenes: Labile defensive
lipids from the glandular hairs of a caterpillar
(Pieris rapae). Proceedings of the National Academy of Sciences 99(May
14):6822-6827. Abstract available at

Further Readings:
Milius, S. 1998. How bright is a butterfly? Science News 153(April
11):233-235. Available at

For pictures of the adult European Cabbage White butterfly, see

May Berenbaum
Department of Entomology
University of Illinois, Urbana-Champaign
505 South Goodwin Avenue
Urbana, IL 61801

Thomas Eisner
Neurobiology and Behavior
Cornell University
Ithaca, NY 14853


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