The Dagger

On Wednesday of last week (6/3), I spotted a not quite 2” caterpillar trekking across the macadam of our outdoor loop trail through Catch the Wind and Explore the Wild. The caterpillar had a black head, yellow-green body, black markings on its sides and a whitish mid dorsal stripe, which included a series of eight “warts,” three of which were more prominent than the others. It was moderately covered with white setae (hairs) with the setae on the thorax longer and brushed forward.

Black head, yellow-green caterpillar with “warts” on back.

Although I didn’t know what it was, what species it was, I thought it distinctive enough and shouldn’t be too difficult to identify later. I was wrong.

I knew it was a moth and figured it to be either a tussock moth or dagger moth. I’m familiar with just about every butterfly in the area that produces a caterpillar of this size and you don’t often see them traipsing across the bitumen.

I started my search in the most excellent guide Caterpillars of Eastern North America – David L. Wagner, which has 1200 photos of close to 700 caterpillars east of the mighty Mississip. I started in the dagger moth section. But, finding no matches for my caterpillar, decided to thumb through the whole volume, some 450 pages of photos. Sometimes, that’s the only way to do it.

On my second or third pass through the book, I noticed one caterpillar which matched the size and shape of my caterpillar, warts and all, but it was far from being green or yellow. It was black with lighter brown markings. The name at the top of the page was Ochre Dagger Moth (Acronicta morula).

Sometimes, you will learn, caterpillars vary geographically. Their colors may be different from region to region and, importantly, from instar to instar (molt). They can molt four or five times before pupating.

I did some internet searching. Since I now had a name to start with, I could search for other “green” ochre daggers. I found several which were very close to being the same color as my caterpillar. They had the same markings, same warts, same setae. The only thing that didn’t match was a pair of red markings that are supposed to be located on top of the head. Apparently, these red markings vary as well. Some of the ochre daggers in the photos on the internet, specifically at BugGuide.Net, have large red markings, some have small red markings, and some have no red markings at all, none that I could make out in the photos.

I can see no red markings on this caterpillar.

Red markings or not, I’m convinced that the caterpillar is an ochre dagger moth caterpillar (Acronicta morula). According to Wagner, the caterpillars consume the leaves of elms, but also apple, basswood, and hawthorn (not many of the latter three here on campus but there are plenty of elms about). They can be found from Manitoba to Nova Scotia and south from Texas to Georgia, which includes North Carolina.

The adult is one of those nondescript, brown and gray moths that you may see flying around your back porch light after sundown.

It’s not a rare species, but it’s the first I’ve seen here at the North Carolina Museum of Life and Science.

1 response to The Dagger

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    Sarah says:

    I just found this 3 days ago in Louisville KY and have been having the most difficult time identifying it!!!!! Thank you so much for sharing this post.

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