While driving through central Nebraska last week, I couldn’t help notice all the fuzzy creatures crossing the highway in front of me. They weren’t raccoons, deer, or even voles. They were tiny little caterpillars, and they were moving FAST.
This was a common site along Nebraska highways last week.
I’m not entirely sure why the caterpillars are on the move, or where they are going. Some internet searching turned up some university extension and similar pages that infer that the caterpillars are simply searching for a good place to spend the winter. That could be true, but if so, they sure don’t seem to be doing it in any organized fashion! There were just as many caterpillars crossing the road from left to right as there were from right to left. It made me wonder if they just kept going back and forth… (tiny little brains.)
As I drove, my scientist mind was spinning, despite my best intentions. I kept track of the land cover types on both sides of the road, trying to figure out what kind of habitats the caterpillars might be leaving or heading for. If there was a pattern, I didn’t see it. The caterpillars crossed the road in places where there were soybean fields on both sides as well as places where there were miles of sandhills prairie on both sides. They didn’t seem to be heading from high ground to low or from tall vegetation to short – or vice versa.
Another one.
My photographer brain was also in full gear, which meant I had to keep stopping to take photos of the little buggers. Fortunately, the roads I was traveling were not very well populated with other vehicles, but I still had to be discreet to avoid uncomfortable conversations. Whenever I heard a vehicle coming I just pretended I was stopped to make a phone call or just to admire the view. Otherwise, I would have ended up having conversations something like this:
“You okay?”
“Me? Yeah, I’m fine.”
“Oh. I just wondered why you were lying in the middle of the highway.”
“Um, yeah. I was actually taking a photograph of a caterpillar.”
“A caterpillar.”
“Yeah.”
“In the middle of the highway?”
“Well, yeah. I wanted to know why it was crossing the road.”
“Is that a joke?”
“No, but now that you mention it, it might not be a bad start to one…”
“So you don’t need any help?”
“No, I’m good, but thanks for asking. I’m just trying to get some pictures.”
“In the middle of the highway. On your belly.”
“Well, yeah. You see, I’m a prairie ecologist.”
“Oh! Why didn’t you say so? Carry on then…”
Anyway, I did manage to get some photographs of the commuting caterpillars. I’m glad I did because seeing them up close made me realize there were several different species of them making the crossings. I also (I can’t believe I’m admitting this) timed them to see how fast they were going. What? I was just curious…
I wish the caterpillars well on their journeys. There were surprisingly few smooshed caterpillars on the road, so I’m assuming the majority made it across the road. I hope that means they found a nice place to spend the winter, or whatever they were looking for.
I also hope no one saw me photographing them.
You probably don’t care, but in case you’re wondering, the caterpillars were making the 32 foot trip across the highway in about 80 seconds. If my math is correct, that means they were traveling about 4.8 inches per second. That’s moving right along for a tiny critter with stubby little legs!
The Prairie Ecologist 
A better question, “Why did the caterpillar cross the road?”
I’m not so sure that among your pictures there is more than one species of caterpillar, but rather, color variants of a single species — perhaps rather poorly named Salt Marsh Moth Estigmene acrea – http://bugguide.net/node/view/3242/bgimage
James, I had that thought as I prepared to post this, but didn’t realize the Salt Marsh moth caterpillar was so incredibly variable – wow! I think you’re likely right (of course). It makes me want to go back up and get some better photos… Any other info or guesses on why they’re on the move?
And that’s a pretty rough road for a caterpillar!
I saw the same thing in central Kansas last week. In this case, the caterpillars were leaving a field of sunflowers and heading across the road. Lasted for a day or two. I didn’t stop for photos.
The best part is — you live where people stop and ask if you are ok. Do you know the species of butterflies and moths that will appear next spring?
Joanne – see James’ comment. If he’s right (and he usually is) it is the Salt Marsh Moth.
I too marvel at how fast tiny creatures like insects move. I think the thing that amazes most is how butterflies migrate. I was out on the walkway to the morning glory spill at Lake McConaughy on a very very windy day and saw a monarch butterfly hanging on mightily to the wooden plank walkway while the wind was batting it around. I stooped to scoop it up and bring it to a less windy spot and was impressed at how strongly it was hanging on with its very fragile looking feet and legs. I did “rescue” the critter and let him go in a more serene setting only to see him/her immediately fly up into the wind and manage to make some headway. How do they do it?
Chris
I think you need a bumper sticker that says ” Proceed With Caution, Prairie Ecologist at work”!! with a flashing yellow light.
Yes, some of us are interested in the critter’s speed. I couldn’t believe it, and checked your math — same answer! How big were the caterpillars?
Chris – the caterpillars were about 1.5 to 2 inches long.
I can’t believe that I have to tell a respected PrairieEcologist about the most important aspect of these caterpillars. I’m from Wisconsin and everyone there knows these fuzzy animals, wooley bears, are the true predictor of Winter weather. The earlier you see them running across the road the worse the winter will be. I’ve never seen them this early; I’m tuning up my snow blower!
I’ve seen Pipevine swallowtail caterpillars scurrying across the black groundcloth that I have laid down at my nursery. They can move pretty fast also. Apparently they are searching for a place to build their chrysalis. And if you see where Monarch caterpillars make their chrysalis, you know they can make quite a journey from the milkweed (Asclepias) plants that they were feeding on.
Yep, I agree…caterpillars are looked at here as winter fortune tellers…the earlier and the more you see…the closer and heavier the winter. We’ll see….even though I don’t really want a “bad” winter, I still try to avoid the fuzzy guys when on the road:).
I loved this and I am going to remember that “I’m just on my cell phone, don’t want to text and drive” thing next time I am out taking pictures in an unusual place, and a car comes along.
Where is the Prairie Geologist to tell us about the colorful gravel that made that road bed? And the caterpillars were interesting too!
There are times of year that I think roads should have huge Detour signs. 1) Turtle egg-laying 2) Caterpillars crossing 3) Frogs during the rain 4) Butterflies in flight. Hm, well except for Winter, that pretty much covers everything! Every time I hit a bug I flinch.
If I came across you on the road, I would stop and take photos of you. :)
I think nature would select for a fast caterpillars in this case :)
I have observed a similar phenomena in Arizona. I’ve been down here coming up on 3 years now, and once a year (I haven’t made note of the exact time — I am not sufficiently ‘scientist-y’, you see — but I would say late August, early September) on a drive I regularly take on a somewhat remote stretch of freeway I suddenly notice ‘yellow things’ on the road; then the next thing I notice is that many/most of them are moving — and many/most in the same direction; then I realize, yup, caterpillars. That would be at approximately the same moment I’m quite confident that smooshing is taking place, because there are a LOT of them — the smoosh rate has to be quite high. And on this stretch of highway there is no stopping and crawling on one’s belly for photographs . . . the posted speed limit is 65 mph, which means everybody is actually doing 80+ (it’s an Arizona thing). I’m sort of with anastaciast, I wish there was a detour. If I knew the exodus was taking place, I would definitely choose a different route. But I’m guessing there is little rhyme or reason to the timing — something in their tiny little brains says it is time to go and off they go. It is not a ‘grass is greener’ thing — both sides of the road are equally brown. ;-{)>
We are seeing a lot of those caterpillars here in Wisconsin too! We call them Woolly caterpillars and every autumn we see them crossing roads, sidewalks and trails. We always say there is going to be a harsh winter ahead if there are a lot of them, so, judging from the numbers, I think we are in for another doozy of a winter!
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Omg! My son and I are traveling south on interstate I-25 north of Casper Wy right now! We’ve seen them for 50 miles! What the?!?!?
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