No Building Permit Required


While visiting the Attwater Prairie Chicken Refuge, I found this bit of complexity at the intersection of two trails.

Lincoln Logs hadn’t come to mind in years, but that’s exactly what the construction resembled: an oddly designed but well-built home made of tiny logs. In fact, it is a home: one belonging to a member of the Psychidae, or bagworm family. 

Bagworm moth caterpillars weave silk cocoons around themselves, and then reinforce the silk with bits of twigs, leaves, or stems. The construction materials determine the final appearance of the houses, which also are called ‘cases.’

Bagworm moth cases can be attached nearly anywhere; this one dangled from a substantial sunflower stalk. Oddly, the cases more closely resemble RVs than suburban homes; the caterpillars are mobile, carrying the case with them as they hunt for food. They feed from a hole in the top of the case, and expel waste from a smaller hole in its bottom.

Growing bagworms expand their home by adding more twigs, leaves, or stems. Emerging from the top of the case to collect building material, they cut it to size before attaching it to the top of the case.

Both males and females spend most of their lives living inside their cases as caterpillars. After pupation, females remain in the case, while males leave to seek females with which to mate. After mating, females lay their eggs in the old bag. Once the larvae have hatched, they leave the case, seeking a suitable spot to build their own home.

Whether Einstein ever found himself contemplating a bagworm case, I can’t say, but his words ring true as I contemplate this one:

The important thing is not to stop questioning. Curiosity has its own reason for existing. One cannot help but be in awe when he contemplates the mysteries of eternity, of life, of the marvelous structure of reality. It is enough if one tries merely to comprehend a little of this mystery every day. Never lose a holy curiosity.


Comments always are welcome.

64 thoughts on “No Building Permit Required

    1. Every time I come across something like this, my first thought usually is, “What is that?” Then, I begin to wonder how in the world they know to do ‘that.’ I wonder if this caterpillar has a tiny little tape measure and a teeny-tiny saw in there.

  1. That is the most interesting bagworm case I’ve ever seen. It does remind me of the Lincoln Logs I loved to play with long, long ago. I’ll have to speak to the bagworms that love my mountain laurels – they’re falling down on the job.

    1. Lincoln Logs came to mind first. Then I pondered for a while and decided it looks like the result of Frank Gehry deciding to build a log cabin. That’s certainly a lot of work for a little caterpillar, but of course they don’t have much else to do but eat, sleep, and add on to the house.

    1. I’m often surprised by some people’s lack of curiosity about the world in general, and the natural world in particular. I must say, I also worry about the ways in which children’s natural curiosity gets stifled. I suspect Lily won’t be so constrained.

  2. I’ve stumbled upon these many times over the years. Though I almost didn’t recognize it from the extreme closeup of your shot. Most of the ones I’ve seen have been associated with conifers of one form or another.

    1. Some other people mentioned that association with pines. I certainly was surprised to see it dangling from a sunflower, but I suppose the caterpillar knew what it was doing. There’s nothing like a macro lens to make the details stand out.

      1. Way back in the 70’s when I got my first grown up camera the salesman at the camera store talked me into buying a 50mm Macro lens instead of the faster normal lens. It cost almost as much as the body. But, oh how I loved the shots I could get. I once got nose to nose with a Texas Horned Toad/lizard on a south Texas gravel road. For a lot of years a framed blowup of that shot hung on our livingroom wall beside Avedon’s Snake Woman. . I still miss shooting with that lens.

    1. It was about three inches long. I didn’t have a ruler or tape measure with me, so I used my longest finger to gauge the size, then measured my finger when I got home.

    1. I wondered if the creatures could be found in England, and the answer is yes — several Psychidae species have been recorded there, mostly in forests. Keep your eyes open on your jaunts!

      I smiled when I read in this article that “the last few years have seen a considerable increase in interest in Psychidae among UK lepidopterists, and searching for the often well camoflauged larval cases during the Winter months now regularly fills the gap between Autumn and Spring MV moth trapping seasons.”

    1. Even though this one was well below eye level, it was large enough to attract my attention. At first, I thought it was a grasshopper or some other insect; I certainly was surprised to find this. Other people have mentioned finding them on evergreens; it’s neat that you’ve seen them.

  3. When I was a kid, the city had planted lots of cedar trees in the parks near our home. The bagworms loved to build these tiny RV’s in the cedars, because they were covered in hanging bagworm homes. As a youngster, and a boy at that, we loved to pull them off and stomp them to see if they squished or not, indicating that they were empty or still had a worm inside them.

    What???…it’s just what little boys DID.

    1. Snips and snails and puppy-dog tails — and a tendency to stomp bagworms to see if they squish — that’s what little boys are made of! (Of course, even our sugar and spice crew wasn’t always nice, but we weren’t so fond of squishy things.)

      They do seem to prefer evergreens like cedars. The teardrop shape of the ones covered in bits of cedar or pine are the most common in online photos, but of course this one had to make do with other sorts of building materials.

    1. That rustic look makes me think of the north woods. I wondered if there were any others like this one in the area, and when I did a search on iNaturalist, I found this one that was observed between Victoria and Telferner! You’d best keep your eyes open — they’re obviously around.

      Now I’m wondering whether this form of the case is specific to a certain species. It makes sense, but I hadn’t thought of it before.

  4. The first time I came across one of these little “houses,” it perplexed me. Why wouldn’t it?

    Einstein’s “Curiosity has its own reason for existing” reminds me of Emerson’s line from “The Rhodora”: “…if eyes were made for seeing, / Then beauty is its own excuse for Being.”

    1. Perplexity seems a natural response to a first sighting of something like this. In the process of responding to comments, I’m a little less perplexed about this one’s identity. I’ve come to suspect it may be Abbot’s Bagworm Moth — Oiketicus abbotii . I’ll check it out with BugGuide, but when I looked at the images of the family on iNaturalist, I noticed that all of these log-cabin-ish ones belonged to the genus Oiketicus. It hadn’t occurred to me that variations in the cases would be species-specific; it’ll be interesting to see if that’s the case.

      That’s a good quotation. If only we could get some people to open their eyes; the world might seem more beautiful to them if they did.

      1. I really do agree with you here – getting people to open their eyes to the beauties of the world might be key to protecting our wonderful planet, as well as making them much happier.

    1. Honestly, it would have been enough to see this very intriguing case, but when I found out that these insects haul their houses around with them like a turtle, I was astonished. It seems like it would take enormous amounts of energy to do that, but I suppose it’s all part of a day’s work if you’re a bag moth.

  5. Finally a name for the strange structures that appear from time to time. I’ve never seen an actual moth though. Thanks for identifying the little creature for me.

    1. Apparently they spend most of their lives in the case, so not seeing the moth isn’t that unusual. It would be wonderful fun to spot one emerging from the case, though. If I get back down to that refuge in the relatively near future, I’ll certainly take a look and see what’s happened to it: provided that it hasn’t moved to a new neighborhood!

  6. Cool! How interesting. This did remind me of Lincoln Logs, although, after G.I. Joe & Battery-Powered Remote-Control Godzilla wrecked the cabin.
    Also like that Pick Up Sticks game.
    What a fascinating caterpillar, though, gluing stuff onto his mobile house. That also reminds me a bit of Baba Yaga, a folktale about a witch with a hut on chicken legs, that followed her around.

    1. I loved Pick Up Sticks; that’s a great comparison, although the thought of Godzilla running rampant through the house is pretty darned amusing.

      I hadn’t heard of Baba Yaga. After just a little reading about her and her activities, I think I’ll hope not to meet her in the woods. Any witch that flies in a cauldron rather than on a broom and who steers it with a mortar isn’t to be messed with!

      Here’s something else I learned tonight. It may be that different species of bagworms build different kinds of homes. Photos like this one seem to be limited to Abbot’s Bagworm Moth — Oiketicus abbotii. It makes sense. Certain butterflies prefer different flowers, so why shouldn’t different bagworms use different plants for their constructions?

  7. It is an interesting find and does have a Lincoln Log thing going on!! It always is amazing to see how living things do their constructs. I enjoy most I suppose the woven twigs and platforms that the great herons and wood storks construct. The weave itself is interesting but I always enjoy when some twigs still have leaves or flowers attached or if there is an intriguing acorn shell included in the work. Makes the decor all the more beaufiful. I am not at all familiar with bagworms but what a fabulous job!!

    1. I’ve always been impressed by birds’ nest-building abilities — well, except for some species, like mourning doves, who often throw down a few sticks and let that suffice. But birds that reuse nests, and repair them through the nesting process, and weave complex, stable structures? They’re fascinating. Now and then I’ve found nests that have blown out of trees during storms, and the fact that they survive intact is a testament to the birds’ skill.

      I’ve only seen nests with leaves, flowers, and such in places like gift shops. It never occurred to me that those ceramic or other artificial nests might be replicating nature. Live and learn!

      1. It does look very pretty when a twig with green leaves is woven in or one with a few red berries. That’s one of my favourite things really..when the nest is beautiful. In nesting colonies there can be sequential nesting process. So when one species abandons its nest, another will take if over, or simple snitch a few twigs out of it for their own. I watched that with a cattle egret once stealing from a vacated anhinga nest. The bird seemed so guilty about it too coming out of an area deep within the pond apple, wiggling out a twig then rushing back into the shadows. Cute really to watch.

    1. I’ve gone for years without spotting a Monarch or other butterfly chrysalis during my wanders, so this is a bit of a consolation prize. I think Einstein would have loved this one; he probably could describe the physics of its wonderful construction!

  8. I had the same reaction as many of your other readers, Linda: utter astonishment. Having never heard of bagworms, this seems like a fairy tale too out-of-this world to be true. But the best thing is that it is of this world, which will never cease to amaze and astound.

    1. Mark Twain would agree with you. In Following the Equator, he wrote, “Truth is stranger than fiction, but it is because Fiction is obliged to stick to possibilities. Truth isn’t.”

      In the past day, I’ve come to suspect that various species of bagworms might construct different forms of cases, instead of all of them just using whatever’s at hand. If that turns out to be true, there will be a follow-up post. If I’m lucky, I’ll be able to check on this one’s progress, too — although if it decides to move before I get there, that might not happen.

  9. What a great find. I’ve seen the caterpillars many times but never one of their “houses”. How cool. And Lincoln Logs. So much better and developmentally helpful for kids than video games, at least in my opinion. Erector sets, building blocks (pre-legos), even pickup sticks. While I am always amazed at what nature’s creatures do, I am not surprised. They are very resourceful and creative. A friend of mine has authored a few books regarding insects. You might find his latest interesting.

    1. Thanks for the tip about your friend’s book. At this point, I tend to approach insects on a need-to-know basis; that is, when I find something interesting, I do the research, but for the most part BugGuide, iNaturalist, and a few individuals do the trick for me. I have enough trouble with flowers (and now birds) to add insects to the list of things to really study — not to mention there’s not enough time to take them all on!

      I do have a new suspicion that I need to check out. Most online photos of bagworms show the teardrop shaped ones made of cedar leaves and such. There are very few photos of these little ‘log cabins,’ but it seems all of them belonged to the Abbot’s Bagworm Moth (Oiketicus abbotii). That’s when it clicked: different species may build different homes. More research is required!

      1. I am sure they all do at least slightly different if not completely constructions. Just like they’ll cover themselves with whatever is handy. The book is not so much for identification as just examples of how insects adapt and did so ahead of our observation and use of their abilities. If you are ever interested, I can name a few other authors whose writing is more about how amazing they are in what they do to survive and be fruitfully multiplying. Some of what individual species do just to procreate is astounding.

  10. I love it. A do-it-yourself mobil home. Enjoyed both your photos and words Linda. As for Einstein’s words, a message to live by. BTW, Caddisfly larvae build very similar cases in the water made of sand and small sticks for protection against predators. I suspect the bagworm has a similar purpose in mind. –Curt

  11. Lincoln logs! That’s great! Weirdly, I’ve never thought of the bagworm chrysalis as a Lincoln log creation, though the comparison is obvious. I love them, love finding the little chandelier-like creations hanging in odd places. Maybe they can also be compared to vertical stumperies?

    1. I think there’s an answer to the different forms of the cases. I think that different species build differently. When I looked up their cases to see if I could find another like this one, I certainly did, and most of the ones that resembled this one belonged to the Abbot’s Bagworm Moth (Oiketicus abbotii). Different cases for different species may be the entymological equivalent of different strokes for different folks!

    1. They are amazing, and my hunch now is that the different forms of their cases vary among species. I think this one is Abbot’s Bagworm Moth (Oiketicus abbotii). I’ve not checked that out yet, but it’s on my to-do list.

    1. I see you found Curt’s reference to the caddisfly cases. There’s a hilarious story in Dillard’s Pilgrim at Tinker Creek about them. She searched for one for years, then went for a walk with a kid, who immediately spotted one in the creek.

    1. From what I’ve read, they don’t leave the cocoon. They stick their little heads (and presumably as much of their body as is necessary) out the top of the cocoon, do their construction, and then head back inside.

    1. I mentioned this wonderful Mark Twain quotation to someone else; n Following the Equator, he wrote, “Truth is stranger than fiction, but it is because Fiction is obliged to stick to possibilities. Truth isn’t.” I love that.

  12. Fabulous photograph of a really interesting moth bag!

    I’ve tried to find a male adult Bagworm Moth for years, but no luck yet. When a male emerges to go look for a female, he only lives one to two days. Some day, maybe …

    (I had to have children and then grandchildren in order to continue to play with Lincoln Logs without folks wanting to have me committed. Didn’t help – they still insist I’m not quite all there.)

    1. I found a few photos of the moth online, but there are far fewer than of the bags. You’re not alone in missing the moths — I certainly never have seen one! Now that I know how they live out their lives, I’ll take a look at the next one I come across, just to see if someone’s poking a head out of the top to say hello!

      I never built with Lincoln Logs myself; I was a fan of the red plastic bricks with the green cardboard roofs and white windows and doors.

    1. I certainly was astonished. I stared at the thing a good while before I even started taking photos. I tried showing it to a family who passed by, but they weren’t interested. Silly people!

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