Madrone Caterpillar (Eucheira socialis)
|Trail Making and Foraging Behavior|
|Shelter Building and Thermoregulation|
The madrone caterpillar is
in the high mountainous regions of Mexico where its host tree, the
(Arbutus) occurs. The
caterpillars are present from early summer unit late the following
The caterpillars that comprise a colony, which may number 200 or more,
are siblings and they remain together throughout their lifetime,
and eclosing to the adult en masse. The larvae construct a silken,
nest, within which they rest between bouts of feeding. Adults
from an opening at the bottom of the nest in June. Recent studies
that some populations of the caterpillar are strongly gender biased
as many as 80% of the caterpillars being male.
Trail Making and Foraging Behavior
Eucheira caterpillars leave their nest to feed only under the cover of darkness. The caterpillars become active soon after darkness sets in in the early evening. They follow silk trails to distant feeding sites, where they forage throughout the night and early morning, typically returning to the tent just before sunrise. In the winter, the catepillars forage at very cold temperatures and are able to remain active even when temperatures hover about 0oC. Occasionally the caterpillars are immobolized by sub-zero overnight temperatures and can not return to the bolsa until the sun comes up and warms their bodies.
The larvae of Eucheria
their trails with a pheromone secreted
from the tips of their abdomens and, like tent caterpillars, are highly
responsive to 5b-cholestane-3-one.
tent caterpillars, however, the madrone caterpillars do not recruit to
Shelter Building and Thermoregulation
caterpillars construct their shelter entirely from silk. The
of the nest are so densely woven that the nests will hold water and can
only be penetrated with a sharp knife. There is usually only one exit
which is found at the bottom of the structure. The nests trap the heat
of the sun and warm to temperatures in excess of the ambient
The caterpillars move about the nest adjusting their body temperature
seeking warmer or cooler areas. In the winter, studies indicate
the caterpillars may keep their body temperatures relatively cool
the day to prevent adaptation of their enzyme systems to warm
Such adaptation would hinder their ability to locomote on cold
Occasionally, the caterpillars are immobolized by sub-zero overnight
and can not return to the bolsa until the sun comes up and warms their
Fitzgerald, T. D. and D. L. Underwood. 2000. Winter foraging patterns and voluntary hypothermia in the social caterpillar Eucheira socialis. Ecological Entomology 25:1-10.
Fitzgerald, T. D. and D. L. A. Underwood. 1998. Trail Marking by the larva of the Madrone butterfly Eucheira socialis and the role of the trail pheromone in communal foraging behavior. J. Insect Behavior 11:247-263.
Fitzgerald, T. D. 2001. Night Life of Social Caterpillars. Natural History Magazine 110: 38-42
Underwood, D. L. A. and A. M. Shapiro. 1999. Evidence for division of labor in the social caterpillar Eucheira socialis (Pieridae: Lepidoptera). Behav. Ecol. and Sociobiol. 46: 228-236.
Underwood, D. L. A. and A. M.
1999. A male-biased primary sex ratio and larval mortality in Eucheira
socialis (Pieridae: Lepidoptera). Evol. Ecol. Res. 1: 703-717.
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