Macbeth was hallucinating, of course, when he envisioned the instrument of death before him and uttered “Is that a dagger which I see before me?” It was a bloody dagger. I, on the other hand, was not hallucinating – or if I was, it was a pretty bland hallucination – when I saw a dagger before me. My dagger, which I saweth but a fortnight ago, was an American Dagger caterpillar (not instruments of death unless one attempted to shove several dozen up someone’s nose).
Dagger Moth caterpillars are remarkable looking beasts. It is hard to pass by one of them without exclaiming “what a remarkable looking beast.” They are hairy beyond the norm, about 3 inches long at maturity, and equipped with multiple hair tuft antennae. To be truthful, these larvae are not actually covered with hair. If these structures were true hairs then we’d looking at the world’s most bizarre mammal. They are technically called setae – hairs that are not hairs but hair-like.
The setae tend to be yellow on the younger caterpillars and often turn to whitish gray on the mature worms. My example was a mature beast yet as bright a yellow as the day is long (whatever that means), so it a bit atypical in that regard. The long black antennae-like tufts are called “lashes” (a term made up by the Revlon folks I believe). There are two sets of lashes on the first and third abdominal segments of the Dagger caterpillar and a single lash on the 8th segment. These probably serve as sensory devices rather than beauty enhancement features, but they could be dual function attachments. For instance, I am fairly certain that Beyoncé has never walked into a wall and that we can thank her early warning lash system for that.
American Dagger moth larvae eat a wide variety of tree leaves. In my experience, they seem to prefer maples. Half consumed leaves littering the ground beneath a tree betray their presence long before the critters are spotted. Piles of barrel shaped poops on your car hood will also give them away. When actually discovered and touched, the caterpillars will bat their lashes and withdraw into a characteristic “J” shape. Further harassment will induce them to roll into a ball. They say that the hairs…er, I mean setae…can be irritating, so it’s best not to irritate a Dagger larvae too much lest he “sheddeth his prickly hairs into thee.”
The caterpillars eventually make their way to the ground in the fall and seek shelter under logs or boards. There they will form a cocoon and spend the winter as a pupae. This cocoon incorporates the body hairs into the silken wrap. Beneath all that fuzz, Dagger caterpillars are smooth green gummy worms. If Shakespeare had known about American Dagger caterpillars he would have penned “Beneath dense setae green nakedness we do see-tay.”
The adult moths, which emerge the following spring, are unassuming gray beasts which blend into their surroundings. Like other members of their ilk they possess a cryptic image of a dagger upon their forewings. This image is very obscure, to say the least, but it is the reason behind the family name (there are 70 plus kinds of dagger moths). I’m thinking that bad eyesight was involved somewhere. If Macbeth saw this fuzzy image of a dagger floating before him, he would have said “is that a fuzzy blob I see before me…am I to commit murder by shoving these up the nose of my intended victim?”