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Observations, factoids, funny clips, and lots of bugs and other nature related images.

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It looks like I’m going to need to start watching where I step in my house. Not because there are dog toys on the floor, or rugs waiting to trip me up (although it has been known to happen), but because I have extra critters roaming about. Large, fat, and theoretically grossly squishy if stepped on, caterpillars!

Technically, it was actually my partner who found the unexpected, and quite large, caterpillar lumbering along. I was busily working away on my computer in another room, when he excitedly popped his head in like “babe – there’s a big caterpillar in the house!”. He is well trained at this point to bring unusual bug activity to my attention 💕💕 . “Whhaaat?! I ask in a Scooby Dooi-sh sounding voice. “Really?!” I ask, as Sunday and I rush out to investigate lol. Needless to say, I was not expecting a caterpillar to wander inside the house this time of year (it’s like 30°F outside – brrr), but a caterpillar it most definitely was.

Yellow-striped Armyworm crawling across my floor

Yellow-striped Armyworm crawling across my floor

At first I thought it was a Large Yellow Underwing Caterpillar, Noctua pronuba, – as it looked very similar to the photo in the caterpillar field guide I always use. However, after scrolling through tons of images on BugGuide, one of my favorite resources for double checking my identifications (as you might have guessed by the number of links I add to the further reading section), I am now pretty confident my caterpillar is actually a Cotton Cutworm, Spodoptera ornithogalli. Also known as the Yellow-striped Armyworm.

Yellow-striped Armyworm curled in defensive position after I touched it

Yellow-striped Armyworm curled in defensive position after I touched it

The Yellow-striped Armyworm is native to North and Central America, but is more commonly found in the more eastern and southern US states. It can be a serious pest species of agricultural crops, as it feeds on a wide variety of different plants from cotton and corn, to tomatoes and peppers, to roses and ornamental plants. They will even feed on fruits of many of these plants (not just the leaves) as well as weeds. That’s one versatile caterpillar!

Yellow-striped Armyworm curled in defensive position after I touched it

Yellow-striped Armyworm curled in defensive position after I touched it

Originally I had written-off the Yellow-striped Armyworm as a possibility, because the caterpillar I had in my house didn’t have any stripes on it. However, this is one of those crazy species that has two very different caterpillar phenotypes (=visibly expressed/exhibited features or patterns). The image in my book showed a caterpillar with yellow stripes going lengthwise down its body. My caterpillar, on the other hand, had very distinct triangular spots on its back and didn’t have any bright yellow stripes. Easy to see why I wouldn’t have immediately recognized them as being the same species? Yeah.

Yellow-striped Armyworm with totally different color pattern

Yellow-striped Armyworm with totally different color pattern

So how did I figure out my caterpillar was a Yellow-striped Armyworm and not the similar looking Large Yellow Underwing Caterpillar? Without the very different looking adult moth to look at that is… Apparently the Yellow-striped Armyworm doesn’t get its name from the yellow stripes down its back like I erroneously assumed based on the caterpillar morph I didn’t have. It gets its name from two yellow lines, “stripes”, on its face! Who knew? Well, I guess the lepidopterists (aka scientists who study moths and butterflies) did, but I didn’t - until now anyway lol. The Large Yellow Underwing caterpillar does not have these yellow face stripes, but my caterpillar does. That means I have the spotty version of the Yellow-striped Armyworm :) Detective work!

Yellow-striped Armyworm face with two stripes

Yellow-striped Armyworm face with two stripes

I still don’t know for sure why I had this lumbering caterpillar unexpectedly meandering around my living room floor, but I’m guessing it was hiding in one of my herb pots. I had a bunch of my herbs and a couple pepper plants in large pots outside all summer and recently moved them indoors with all the freezing temperatures. My herbs and peppers are in my living room… As I’d prefer not to have a huge caterpillar destroying my small indoor herb collection I’m trying to overwinter, Mr Armyworm got moved outside. He can keep chewing on something out there, or will maybe decide it’s time to stop eating and go into diapause (insect version of hibernation) for the winter. His choice.

To learn more about the Yellow-striped armyworm, check out:

Yellow-striped Armyworm, Spodoptera ornithogalli, moth (adult) Image from the C.P. Gillette Museum of Arthropod Diversity Courtesy of the Global Biodiversity Information Facility (GBIF)

Yellow-striped Armyworm, Spodoptera ornithogalli, moth (adult)
Image from the C.P. Gillette Museum of Arthropod Diversity
Courtesy of the Global Biodiversity Information Facility (GBIF)


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Written by an entomologist for the enjoyment of all... The goal is to post 1 or 2 new stories every week, so stay tuned!