We've Been Invaded!

They're Everywhere!  -  Photo by Susan L. Davenport

They're Everywhere!  -  Photo by Susan L. Davenport

Tuesday Morning

Tuesday morning started off just like most mornings. I got up and let Toby outside, then went to turn on the tea kettle. As I reached to pull a cup out of the cabinet, I heard Toby barking as if he were after a snake, so I went to check on him. I opened the door of the screened back porch and stepped out, but I didn’t see anything. Toby was standing there staring at me as if he expected me to solve all his problems, but I didn’t know what his problem was. I walked over to him and stroked his head a few moments, then turned to go back inside. That’s when I saw them. Masses of worms were wriggling all over my house.

They were everywhere. It was grossing me out, and my imagination immediately started presenting me with mental images of my family trapped inside a house encased in worm webs. I grabbed the water dragon (aka the water hose) and started hosing down the house. Picture this if you’re brave enough: a relatively old, eccentric woman with her hair standing up in different directions, wearing her nightgown, robe, and fuzzy house shoes hosing the worms off the house while fighting off a hundred-pound Doberman who wants to confront the water dragon. Good thing there aren’t many neighbors; they might have been traumatized.

Once the house was worm free, I headed back inside to finish making my tea. An hour later, dressed and ready to do some yard work, I went back outside, only to discover that the worms were already all over the house again. I couldn’t believe it. How had they moved that fast?

I had seen these worms before in previous years, but I had never seen them in masses like this. There were hundreds of worms in each mass. They moved together as a unit, writhing brown blobs about a foot in diameter sliding across my house. There were millions of them. It made my skin crawl.

I raced into the house, grabbed my camera, and headed out into the yard to take some pictures. I needed to know more about these worms. As I stepped off the porch, a worm dropped off the soffit of the house into my hair. YUCK!!!!! I danced half-way across the yard trying to get the gross thing out of my hair and yelling. Poor neighbors – assaulted once again.

They were in the grass, on the flower pots, on the walls, on the bricks – everywhere! They didn’t seem to sting, at least the one in my hair hadn’t stung me, but I still wasn’t sure they weren’t harmful, if not to me, then maybe to Toby or my house. Were they going to eat the wood? As I stood there watching the masses crawl over my home, I felt something around my ankles. I looked down to discover worms crawling up my legs. YUCK!!!!! I danced and yelled my way onto the screened back porch, hitting at my legs and shoes to get the worms off. That was it. I needed data. The war was on.  

Climbing the Walls  -  Photo by Susan L. Davenport

Climbing the Walls  -  Photo by Susan L. Davenport

It turns out they are Forest Tent Caterpillars (Malacosoma disstria Hubner). They are a native insect that has been common all over the United States and into southern Canada since colonial times. They are prevalent where hardwood trees grow.  In the north, they have regionwide outbreaks that occur every six to sixteen years. In the south, they occur more often, and the southern gum forests in southwest Alabama and southern Louisiana have had continuous infestations since 1948.

The insects favor broad-leaved hardwoods; sugar maple and aspens in the Northeast. In the Lake States, their preference is quaking aspen and oaks. Oaks are also their favorite in the Appalachians and the Central States. In the Midsouth, it is water tupelo, sweetgum, swamp black gum, and cottonwoods and elms in the Mississippi Valley. In the Northwest, they prefer red alder and willow, and here, in Texas they favor oaks. But these insects aren’t purist. After they have stripped the trees, they are more than willing to feed on wild and ornamental shrubs and even the leaves of fruits and vegetables.

I live in an oak forest. I bet you’re beginning to get the picture now, right – if not, check out the Photo Gallery and you can see a picture of the forest behind my house. I was beginning to understand why they were in my yard, but not why they were on my house. They eat leaves, not wood, shutters, and screens. Had they mutated into some weird hybrid worm that eats houses?

There is one generation of these insects a year. Young larvae (worms) appear when the leaves are beginning to unfold. When they are born, the larvae are almost uniformly black, and less than one-eighth of an inch long, with conspicuous hairs. The colony of larvae stay together and move about in a file, following a silk path laid down by the leaders. With each successive molt, the larvae change color. They develop markings of pale blueish lines along the sides of their brownish body, and a row of footprint-shaped, whitish spots on a black background down the middle of their back. When full grown, the caterpillars are about two inches long.

Closeup They're Beautiful  -  Photo by Susan L. Davenport

Closeup They're Beautiful  -  Photo by Susan L. Davenport

The larvae pass through five phases (instars). When they are born, they are usually in the upper part of a tree; later they are more commonly found lower in the crown and on the trunk. (Note, they didn’t say anything about them being on a house. The worms at my house are definitely mutant worms.) When high populations cause food shortages, the fourth and fifth instars move around in search of food. Their movements have caused them to be called ‘armyworms’ by some.

I was thrilled to learn that if I stood under a tree during this infestation, I would likely get a powdery substance on my hair and shoulders. Yes, you deduced it correctly – worm poop. Yuck! Guess where I am not going to be standing for a while.

Five to six weeks after they hatch, the larvae spin cocoons of silk. The silk is colored yellow by a powdery substance dispersed between the strands. Do you suppose they use worm poop to hold their cocoon together? Not very sanitary, but I guess if it does the job … They construct their cocoons in sheltered places, like a folded leaf or a crevice in the bark of a tree.

While in the cocoon, the larvae change to pupae. They emerge as buff-colored moths about ten days later. They have two darker oblique lines near the middle of their forewings. The moths are nocturnal and only live for a few days; long enough to lay eggs. The egg masses encircle small twigs, mostly in the upper crown branches of the tree. They contain 100 to 350 eggs per mass. Within three weeks the embryos develop into larvae that overwinter in the eggs and hatch in the spring.

Flies, beetles, ants, true bugs, spiders, birds, and small animals feed on the caterpillars. I talked to the birds in my yard the entire time I was out inspecting the worm armies. I kept encouraging the birds to eat the worms by telling them how wonderful the wiggly worms would taste, but I didn’t see any birds that appeared to be interested. 


Wednesday morning, I got dressed and went out to check on the situation. It had gotten worse. The caterpillars were all over the screens on my back porch. I discovered I could pop the screens quickly and all the worms would fly off into the yard. It was almost like a game. Sometimes there were so many worms it took several pops, but I got them all clear. Yeah! Then I noticed that there were worms inside the screens as well, crawling on the floor of the porch. I don’t normally like to kill creatures that are just doing what comes naturally, but these worms had pushed me too far. I stepped on the first one, and it made the most satisfying ‘pop’ sound. Pop! Pop! Pop! There were worm bodies all over the porch by the time I finished, and I didn’t feel guilty at all. (Driven to the dark side by worms.)  I killed every worm I could find on that porch, and when I had finished my murderous rampage, I brushed my hands off and went back into the house to celebrate.


The research I did suggested that these caterpillars were relatively harmless and that the trees they used as a food source usually had no problem recovering. I decided the worms were too widespread to poison. Besides, the poison that would kill the worms would also kill the other good bugs in my yard. I didn’t want that.

When I got up Thursday morning, I went out to the porch expecting to have to pop the screens and stomp the worms again, but they were gone. There were a few stragglers here and there, but most of the caterpillars had disappeared. I went out in the yard searching for them, but other than a single worm who descended on a silk thread from a tree (he was aiming for my hair), I didn’t see very many at all. What happened to them? Had bats eaten them in the night? Had the birds gotten them when I wasn’t looking? I don’t know. I don’t even care; I’m just thankful my home is no longer in danger of being encased in worm webs. Now my over active imagination can take a break from worm horror images and focus on my novel instead. Life is good.