Eastern Tent Crawlers are having a family reunion in the Lowcountry this year.
This insect usually goes unnoticed at this time of year, but every few years they come to celebrate. You may have noticed them clumped together on logs or lost on the sidewalk. These hairy little things are 1 to 2 inches long with white patches on their backs and cobalt blue patches on their sides.
They hatch in late winter to early spring and feed on trees such as wild cherry and maple. They spin a silken web in the crotch of branches, much like drop webworms. However, fall webworms hatch later in the growing season and build webs at the end of branches. They are more common in the landscape than eastern tent caterpillars.
Eastern tent caterpillars molt five times, increasing in size with each molt. They hang around the web for protection and expand it as they grow. Caterpillars are juveniles in the order Lepidoptera. Like most teenagers, they eat everything in sight. They have now reached their maximum size. It’s time they grew up. That’s why we see them wandering through the Lowcountry.
It’s easy for insects to grow up. They simply leave the nest in search of a place to spin a cocoon. They go through the pupation stage, an idle stage in which they turn into a tawny moth. The adults will not damage trees. They will spend the rest of their lives looking for a mate to lay eggs for the next year. The female can lay up to 400 eggs. The larvae that hatch the following year are social and stay together to build another web.
Why are there so many oriental tent caterpillars this year compared to previous ones? It could be due to the weather or the lack of predators. Lots of things feed on them, from parasitic wasps to fungal diseases. The predator-prey relationship often runs in such cycles. As predator populations increase, caterpillar populations decrease. When there are fewer caterpillars, prey populations begin to decrease. An increase in caterpillars follows.
Birds eat them too. While adult birds eat fruit from trees and shrubs, insects are a primary food source for their young. Caterpillars are a rich source of protein. In the broader sense of nature, insects are generally indispensable. Plants are the first trophic level that converts sunlight into chemical energy in the form of carbohydrates. Insects are the primary herbivores, consuming plants and passing energy up the food chain. Eastern tent caterpillars are not only for birds, but also for mammals. Things like raccoons, mice, and bats will eat these protein-rich crawlies. From this point of view, having bugs around is a good thing.
Once we see eastern caterpillars crawling down our driveways or crawling over the hood of a truck, they stop eating. They just want to find a spot in the foliage or some other dark and secluded spot that they can call home for about three weeks. Once they have finished pupating, they emerge as moths to mate or possibly be eaten by a bird.
In general, eastern tent caterpillars will not kill a tree. Even if they defoliate it, the tree will recover, although this can stress the tree. You are unlikely to see this level of damage in the landscape. However, if you must control them, you must catch them early in their life cycle. Watch for webbing in branch crotches in late winter through early spring. If you can remove the nest, the problem is solved. The net will be filled with caterpillars and excrement. If this is too rough, an insecticide can be used. A very safe product is Bacillus thuringiensis var. kurstaki, also known as Bt. This bacterial protein is only toxic to caterpillars.
The caterpillars are protected in the net. Apply the product to the foliage around them where they will consume it when they come up at night to feed.