What's that thread-spinning, seahorse-like worm/caterpillar?

Asked July 3, 2019, 9:26 AM EDT

While out in the backyard, this strange looking seahorse-like creature dropped down in front of my face near a large maple tree. I recorded some video as the thread-spinning worm/caterpillar danced around in front of me and posted it on YouTube. https://www.youtube.com/watch?v=LfaxxYBrll8 What's that worm/caterpillar?

Ramsey County Minnesota butterflies tent caterpillar caterpillar identification swallowtail caterpillar

14 Responses

There are many caterpillars in Minnesota and your picture is a bit blurry.
Here is a list of common ones https://files.dnr.state.mn.us/mcvmagazine/young_naturalists/young-naturalists-article/butterflies-and-moths/mayjun2016_young_naturalists.pdf

I am inclined to think this is a tent caterpillar.
The branch in the picture is not a maple. The pictures show how to look for the evidence on the leaves and branches and suggest management strategies although in most situations, nothing should be done.
Thank you for contacting us.

Good morning,
A second Master Gardener looked at your pictures and believes this is a Cankerworm based on its behavior and appearance.
I enclose some excellent information for you.
I hope this helps.
Best wishes to you.

Although the tree in the background is a black walnut, I believe, the tree directly overhead is a very large maple. If you watch the video, from which the 2 captured frames/blurry pictures came, you'll see that this worm or caterpillar that dropped down in front of my face looks nothing like an inch worm or a tent caterpillar. It looked like a seahorse - it even had a white fuzzy mane-like thing on its head. Much larger than an inch worm and about the color of a gray squirrel with some brownish color mixed in - it kind of matched the color of the bark on the trunk of the maple.

I agree with my colleague that this is a cankerworm but please put some in a ziplock bag and bring to many farmer's markets or the Arboretum for so that someone can take a closer look.

I saw one of these things one time and have never seen any others before or since. This thing was about the size of my pinky finger. Do cankerworms get that big? The cankerworm images I've viewed, including the one you've provided, appear to show greenish coloring. This thing was grey and brown - no green.. Also, as you can see in the previously attached frame from the linked video, this thing had white furry fluff attached to its head. Do cankerworms grow white stuff on their heads?

This thing does not resemble anything I've seen before in my 60+ years living in the Twin Cities. Not far from where I spotted this thing, there's a compost bin. Is it possible this thing hatched on some fruit or vegetable scrap grown in some other part of the world? The closest thing I've been able to find is the attached image of a sand worm in Hawaii.

It didn't look like any of the caterpillar pictures in any of the links you provided. I watched this thing flying around my head, spinning and dancing on a thread, for about 10 minutes. Apparently, caterpillars have 3 pairs of legs. This thing had 2 spindly horse-like front legs and 3 spikes near the tail.

Caterpillars have two kinds of structures (tentacles on the head or osmetrium on the prothoracic segment behind the head). The osmetrium secrete a stinky material to deter predators. The Black Swallowtail Butterfly in Minnesota belongs to the papilionidae family of butterflies that has this structure.
I hope this helps

After searching through hundreds of frames of video, I think I provided a reasonably clear picture of the worm-like creature I hope to identify. For your convenience, I'll try to tweek the image a bit and attach it again to this reply. The worm-like thing I saw looks nothing like the caterpillars that produce black swallowtail butterfles.

Thanks Bob, that's close, but I'm pretty sure the one I saw was more like a couple inches or longer. Even a 2-inch worm dancing around was pretty difficult to capture with my pocket instamatic camera. I think if it was only 3/4 of an inch, I would have got nothing at all. Also, mine has this white furry stuff coming out of what looks like the back of its head. Other than that though, it does look similar to the spanworm moth.

Thanks I will forward this to Bob who is away at this time.

I think this may be the caterpillar you saw. It is very unusual and not seen this far north so it escaped our usual Minnesota filters. Click on images. See: https://bugguide.net/node/view/497/bgimage

Thanks Mary. It was definitely something along those lines. It seemed to be dangling from a thread possibly somehow connected to the white fluff on its head. I don't see any images of the Phyprosopus callitrichoides - Curve-lined Owlet that show it dangling from a thread or with the white fluff attached.