CAN BE FUN TO WATCH
June 10, 2002
I asked one of my daughters if I should run an updated version of
the following previously published column, she said, "What person
who grew up in the South doesn't remember having one of those caterpillars
walk up an arm or over their fingers when they put them in the caterpillar's
path? Every child should be exposed to caterpillars! I think this
may even get some people out there looking at these caterpillars to
see if they really follow the silk paths."
I was prompted to recycle the column by my neighbor who claims she
does not like to see the tent caterpillars I leave unmolested in trees
in my front yard. She insists they crawl to her yard and eat the leaves
on her trees. I think she's right that some of my caterpillars visit
her yard, but not that they feed on her trees.
Tent caterpillars build their silken nests in early spring in the
forks of cherry or apple trees and eat the leaves when they appear.
Many people probably feel the same way I once did and my neighbor
still does--determined to destroy any caterpillar tents found on such
trees in their yard.
This year I found two tent caterpillar nests in the yard in a cherry
tree. In former years, I would have decided that the constructed nests
and their engineers must go. A gasoline-soaked rag on a long pole
could be used to burn the nest, or the nest could be sprayed with
insecticide. The first is reminiscent of a gladiator sport; the second
releases poison into your yard. Neither is appealing. But I have given
up doing this sort of thing anyway. I would rather watch these enterprising
The eastern tent moth lays her eggs on the tree in early summer and
dies soon thereafter. The caterpillars hatch the next spring and become
social larvae that cooperate in building the nest and seeking food.
They leave the nest during the day, traveling to the ends of limbs
to eat buds or leaves. I observed that each caterpillar left a trail
of silk when traveling along the limbs. Caterpillars use their mouths
to make silk from silk glands, which are modified salivary glands.
Other caterpillars passing over the same limb follow the strands of
silk left by earlier travelers. These silk highways contain invisible
chemicals called pheromones, which are released by many animals for
communication of various sorts, leaving road signs imperceptible to
Using their pheromone-laced silk thread, tent caterpillars give notice
to their siblings when they find an area on the tree where the eating
is good. Experiments have shown that when a caterpillar encounters
two thread trails along a limb, it will almost always pick the one
along which a well-fed caterpillar has traveled upon its return to
the nest, rather than a thread used by an unfed one. Upon finding
a source of food, a caterpillar advertises the fact to its nestmates.
Electing to spare these caterpillars provides something more fascinating
to watching leaves grow on a black cherry tree.
By mid-May the caterpillar numbers appeared to be decreasing and part
of the nest in the tree looked destroyed. Did the wrens or brown thrashers
that were feeding babies around that time find the perfect food source?
What's left of the old nest is still in the cherry tree but the caterpillars
are gone, having moved on individually, each to build a cocoon where
it will stay for about three weeks as a pupa and emerge as a small,
reddish-brown moth. I'm sure some of those that left made a trip to
my neighbor's yard, where they may have been treated ruthlessly if
discovered. However, I bet that on the way some served as food for
a few birds, lizards, and other animals I would sooner have around
than those few extra cherry leaves.
Although it will mean the loss of a few more leaves next spring, I
hope some of these backyard visitors make it through the moth stage.
The other animals in the neighborhood probably hope so too.
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