Forest Tent Caterpillars

Subject: Moth or caterpillar ?
Location: Lake Jackson Tx
April 3, 2016 2:34 pm
Spotted a very large batch of worms on a tree here on the Texas gulf coast,
Wondering as to what they are, moth, caterpillar or butterflies…. Just curious, thanks in advance!
Signature: Curious Rae

Eastern Tent Caterpillars
Forest Tent Caterpillars

Dear Curious Rae,
Your image of a group of Eastern Tent Caterpillars as well as a marvelous close-up of an individual are an excellent addition to our archives.  Folks wanting to make identifications can view documentation of both details of the individual and the group aggregating behavior for the species.  You can find out some wonderful information on the Eastern Tent Caterpillar on the State University of New York at Cortland site devoted to Social Caterpillars maintained by Terrence D. Fitzgerald where it states:  “In terms of complexity of interactions, eastern tent caterpillars stand near the pinnacle of caterpillar sociality. The adult moth lays her eggs in a single batch in late spring or early summer.  Oviposition is limited to cherry, apple and a few other rosaceous trees.  The egg masses contain on average 200-300 eggs. mothEmbryogenesis proceeds rapidly and within three weeks fully formed caterpillars can be found within the eggs. But the small caterpillars lie quiescent  until the following spring, chewing their way through the shells of their eggs just as the buds of the host tree begins to expand.first tent  The newly hatched caterpillars initiate the construction of a silk tent soon after emerging.  The caterpillars typically aggregate at the tent site for the whole of their larval life, expanding the tent each day to accommodate their increasing size. Under field conditions, the caterpillars feed three times each day, just before dawn, in the evening after sunset, and at mid afternoon. During each bout of feeding the caterpillars emerge from the tent, add silk to the structure, move to distant feeding sites en masse, feed, then return immediately to the tent where they rest until the next activity period. The exception to this pattern occurs in the last instar when the caterpillars feed only at night. The caterpillars lay down pheromone trails to guide their movements between the tent and feeding sites. The insect has six larval instars.  When fully grown, the caterpillars disperse and construct cocoons in protected places.  The adults emerge about two weeks later.  Mating and oviposition typically occur on the same day as the moths emerge from their cocoons and being completely spent the females die soon thereafter.”

Eastern Tent Caterpillar
Forest Tent Caterpillar

Update:  April 5, 2016
Thanks to a comment from Ben, we agree that this is a Forest Tent Caterpillar,
Malacosoma disstria, a different species in the same genus.  According to BugGuide:  “Larvae: dark-gray to brownish-black background body color, highlighted by broad, pale-blue lines and thin, broken yellow lines extending along each side” and “Eastern Tent Caterpillar (Malacosoma americanum) has an unbroken cream/white line along its back, and a dark face.”

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