Fully grown cecropia caterpillars are over four inches long and covered with rows of colorful spine-covered tubercles. Their body color varies from pale yellow to blue-green to dark green, depending on age and how recently they have molted (the caterpillar in the photo is not fully grown). Despite their large size and striking appearance, these caterpillars are rarely seen. This is partly because they spend most of their life feeding on leaves high in trees where they are difficult to spot, but also because there has been a notable decline in numbers of these and other large moths over past decades.
The reasons for this decline are still being debated. Habitat loss and light pollution may play a role, but one of the more likely causes is a parasitic fly that was originally introduced in the early 1900s to control gypsy moths. Unfortunately, this fly does not restrict its attacks to gypsy moths and some studies have shown it heavily parasitizes cecropia caterpillars, as well as caterpillars of many other large moths.
Cecropia caterpillars feed on the leaves of non-oak hardwoods such as maple, willow, box elder, black cherry, apple, ash and more. There is only one generation per year, with caterpillars taking approximately two months to reach full larval maturity and form their cocoon. The cocoons, which are brown and pointed at both ends are often placed on bare twigs in trees, but cocoons are also constructed in grass and leaf litter at the base of host trees. These insects overwinter as cocoons and emerge as moths in late spring to early summer.
With a wing span of six inches or more, cecropia moths are one of the largest moths in the country. They belong to a special group of moths known as giant silk moths. Because they fly at night, cecropia moths are not brightly colored like butterflies, but they are still beautiful with their striking rusty red and brown wing pattern. Soon after emerging from their cocoon, female moths climb to a suitable location and begin releasing pheromones that are carried away on wind currents. Males, which have oversized antennae with which to “smell” these pheromones, can detect pheromone-producing females from more than a mile away. Adult moths do not feed and live only a couple of weeks, just long enough to mate and lay eggs.
See Bug’s Eye View No. 1 of 2017 for information on Polyphemus moth, which is another giant silk moth, one that seems to be much more common here.
Also, here is a link to an article on “Moth Decline in the Northeastern United States.”
You might also enjoy seeing the giant cecropia caterpillar costume they use at the Festival of Butterflies in the Kansas City Botanical Garden (scroll down to 10th photo).
It’s like those giant dragon costumes they have at Chinese New Year Parades.
Blake Layton, Extension Entomology Specialist, Mississippi State University Extension Service. The information given here is for educational purposes only. Always read and follow current label directions. Specific commercial products are mentioned as examples only and reference to specific products or trade names is made with the understanding that no discrimination is intended to other products that may also be suitable and appropriately labeled.
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