Are There Differences In Tent Caterpillars?

by Brenna Spear

This past 2012 summer I worked as a naturalist giving programs for people multiple times a week.  I also was working as a visitor services associate when I was not giving programs throughout the week.  An astounding number of visitors would ask a question about “something is doing damage to the trees on my land, whether it’s a disease, or insect damage, can you help me identify what is wrong with my tree(s)?  Most visitors at this point would have done a small amount of research or investigating.  At this point if the visitor had seen or found tents and some sort of caterpillar  on their tree they, usually, could narrow it down to some sort of tent caterpillar, so the number one question I heard the most was how can I tell the difference between an Eastern Tent Caterpillar and a Forest Tent Caterpillar? 

                The Eastern Tent Caterpillar (ETC) and Forest Tent Caterpillar (FTC) both are native to the United States and emerge during bud break in the spring, but anything beyond they are remarkably different.  For instance the ETC does live in tents within a host tree such as Prunus (cherry) and Malus (apple).  The ETC tends to crawl around and eat on its own without all the other tent caterpillars around, but goes back to the tent for rest and protection.  The ETC is also covered with small brown hairs and a row of blue spots along the side with a stripe of white down the center of their back.  

Nevertheless, the FTC does not build tents within trees and they tend to stay in groups while feeding and follow each other up toward the top of their host trees such as Quercus (oak), Acer (maple), and Populus (aspen).  These tent caterpillars have a brownish body with a row of white key hole shaped spots along their back with a bluish line along either side of the key hole pattern.  After helping and explaining the differences between the ETC and FTC to visitors they were able to learn which tent caterpillar they had on their tree.  Once they had the previous information it was easy to guide and help them toward ways to they wanted to deal with the tent caterpillars.  

                I believe this is a relevant topic, because an astounding number of people come into various centers around the United States, wondering what is happening to the tree, which has been on their land for years, but is now covered with one insect.  When they look closer and see caterpillars on their tree knowing the difference between a an Eastern Tent caterpillar and Forest tent Caterpillar can help a landowner in deciding what to do, or if they even need to do anything at all.  It always makes me feel good when a landowner takes the time to come in and learn what is happening to their trees, because you know they first took the time or realized there was something strange going on in the first place to the trees on their land.