2015 August 22

Here’s the situation. I’ve been accumulating pictures of huge, ugly cutworms for some time now. And it’s high time I did something with them. I’ve been putting it off because identifying cutworms to species is kind of off-putting. They are the classic “generally tubular eating machine”, and they aren’t exactly rich in distinguishing features, so going through the guides is an excercise in frustration over some frankly unattactive insects. But, on the other hand, I suspect the average gardener doesn’t much care what the exact species is – they just want the buggers dead, dead, dead. And saying, “It’s a cutworm, you should feed it to the chickens, if you have any”, is likely to be sufficient for most purposes. So, in that spirit, let’s see what we have here.

Let’s start with the most recent one, that I think Rosie found in the garden on May 16, 2015. Unfortunately, I didn’t take the pictures until the next morning, and it had gone prepupal on us. It turned much darker and more greasy-looking than it was when she found it, and was pulling itself into a pupa shape.

Anyway, it pupated just shortly after this, and we kept it in a jar. And then when it emerged about two weeks later, sometime around June 4, 2015, we didn’t notice it right away until after it had fluttered around in the jar long enough to beat up its wing margins.

Anyway, if I had gotten the pictures before it started pupating, it would have looked more like this one from November 6, 2008. Note that this was almost seven years ago, and I was still using my old point-and-shoot camera at the time, so the picture quality is not that great.

It’s still good enough to see the markings, at least. We can also see the size of it. The graph paper it is on is an engineering pad, and the grid is 5 squares = 1 inch. So the caterpillar is about an inch and a half long.

Now, even though the one in 2008 was found in November, and the one in 2015 was found in May, they could still easily be the same species, because a lot of cutworms overwinter as nearly-grown caterpillars. They could also easily be different species, though, seeing as how a lot of other cutworms do the same thing.

Incidentally, this habit of overwintering as mostly-grown caterpillars is one of the things that makes cutworms so aggravating in gardens. They hibernate in garden soil, and come out looking for a snack right about the time that your young seedlings have sprouted. They then cut off your new plants right around ground level. Which of course usually kills the plant. To add insult to injury, they then often don’t eat the whole plant that they cut off, instead moving on to the next one and shearing that off. And spraying insecticides isn’t all that effective against cutworms, because they are underground where the insecticide can’t reach. The first time I posted about cutworms, a commenter told me about a protective method that he says does work, though. If you get a bunch of cheap, disposable plastic cups, and cut out the bottoms, you can then push them partway into the ground around the seedlings that you want to protect from cutworms. The cutworms don’t like to climb over obstructions, and can’t easily dig under them, and so they don’t get at the plants.

Cutworms tend to be fairly large (meaning that they can cut off even quite large seedlings), and come in a small variety of unpleasant colors. Like this one from May 21, 2011:

Or this black, greasy-looking individual from May 7, 2010:

Or this gangrenous greasy green one[1] from June 21, 2010:

Or this dirty gray one, also from June 21, 2010:

And since there are several species, they are never out of season, like this one from July 31, 2010:

Aside from the plastic cup trick, you can knock them back a lot by tilling the soil in your garden thoroughly early in the spring, which either buries them so deeply they can’t dig out, or exposes them to the elements and predators. Birds love them. I bet that turning chickens loose in the garden for a while before planting will do a number on them as well. And if you see any beetles like these or beetle grubs like these, let them alone, because they like to eat cutworms (and also slugs).

[1] Oh, great green gobs of greasy grimy gopher guts . . .

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