When I first came upon a clump of white fuzz sticking to a cluster of Black Walnut leaves hanging over the trail, my first thought was “oh, the fall webworms must be starting up.” Even when I stopped to give them a closer examination, and noted there were several tight groupings of pubescent caterpillars engaged in group feeding, I said “oh, the fall webworms must be starting up.” Though I noticed that there were no actual webs to go along with these webworms, I still stuck to my automated mental response. Webworms, surely…webless webworms, or worms currently without a web, but webworms none-the-less.
Unfortunately, the webless part was difficult to overcome. But, they looked so much like webworms that it was hard for me to clear my mind for anything else. Every avenue of inquiry led back to the same answer.
I will admit to getting stuck, from time to time, in such mental loops. For instance, the water pump at our cabin went out recently and I assumed it was due to a power surge that tripped the breaker. I flipped the breaker switch once with no result. This should have confirmed that electricity was not the issue, but I insisted on flipping it again and again and again for good measure, just in case. All my logic roads led back to the breaker and I was left helplessly flipping the switch back and forth like a trained monkey looking for a peanut reward. (It turned out to be a clog at the well pump head.)
I finally did a web search (go figure!) with the keywords “webworms without webs” just to quell my obvious confusion on the caterpillar question. I was hoping to find an entry that talked about how a webworm colony starts off without a web or that there are rare occasions when they don’t build a website. No such luck. While Webworms will hatch out in a mass, they immediately set about wrapping a silk bag around a bunch of leaves and will feed within the protective folds of the structure. As the colony grows the web bag expands. The larvae do not leave the confines of the web until they leave the colony to pupate. In other words, they are never truly webless until their last stage.
It was a random on-line picture that finally cleared the cobwebs from my head. The communal fellows pictured here were early stage Hickory Tiger Moth caterpillars. This species starts off in a colonial mode but the individuals go their own way after a fairly short time. One by one they drop from the main tree via a silk line and start anew and alone. By the time they are ready to pupate later in the summer, they bear little resemblance to the lightly haired worms of their youth. The larvae take on the appearance of a dirty white toothbrush with a row of stout bristle clusters running down their backs. Tufts of black setae will project from the front and back ends and the alternate name of Hickory Tussock Moth will become suitable. As newly emerged caterpillerets, however, they look like…well, fall webworms.
It might seem odd that Hickory Tiger Moths would be feeding on Walnut – especially given the fact that Fall Webworms love Walnut. But, like many moth larvae, they are eclectic in their tastes and will feed on a variety of nut trees as well as a number of non-nut trees. “Nut ‘N’ None-nut Tree Tigers” sounds rather awkward, so we must accept the “Hickory Tiger” name and move on.
After having said all of this, I will admit that the identity of these creatures was not really all that crucial. It was their neat side by side ordering that initially attracted my attention. Even though the larvae were not especially interesting as individuals, as a gang of precision leaf munchers they were eye-catching. The only reason I needed to find their true identity was so that I could justify this post this with a solid species label (I just HATE not knowing what something is before I pretend knowing something about it).
NOTE: I am including a photo below & here of an actual group of Fall Webworms that I took after posting this entry. If nothing else it might help plead my case for caterpillar confusion (see the webs…).