What's That Bug? does not endorse extermination

Inchworm in dirt cocoon?
September 9, 2009
This creature was found on our kitchen counter early yesterday morning. My wife thought it was a bit of dirt (like a small, dried chunk of mud that fell out of a groove in the tread on the bottom of a tennis shoe). Then a small dark-brown head of what appears to be a worm protruded approximately 3mm, and the “dirt cocoon” inched it’s way along in roughly 0.5-1.0 mm increments, moving along just like an inchworm does. The head end extends out 1-3 mm, then it drags the “cocoon” along behind it.
The “cocoon” appears to be made of fine particles of dirt (very fine particles like silt) or maybe wood or paperboard (like cereal box material).
The cocoon is open at each end, slightly fluted (like the mouthpiece of a trumpet), and the “worm” inside can stick its head out of either end.
It seems to be quite shy, as most of the time it stays inside the cocoon, motionless. When taken out of the plastic bag (with a smallpiece of moistened paper towel kept in the zip-lock bag) and set out free on the table, if we are very quiet it will stick its head out after a few minutes and start to inch along.
I might be able to take a video of it moving, using our ditigal camera, if that is of interest (although like all videos the file size could be too large to send easily, and the resulting video does not have the best resolution/clarity). Let me know if you would like the video and I will make one.
We would be most appreciative if you can identify this creature for us. We will make donation to support the website as soon as this is submitted.
Thank you.
Newhall, California

Case Bearing Moth Larva

Case Bearing Moth Larva

“How does this work?”, or “What happened to my submission?”
I’m wondering how this works. When you, BugMan, or BugMan’s proxy, reply to a “What’s That Bug” submission, does the submittor receive an email notification that you have responded? Or does the response only appear on the website and the originator of the submission needs to check back on the website to see if a response has been posted?
Also, gving the benefit of the doubt, I made a $20 donation immediately after I submitted my question (subject: “Inchworm in dirt cocoon?”, submitted 2009-09-09 circa 17:30 Pacific time US), but I see a few submissions that were made after mine have already been answered on the website, whereas mine has not been replied to as yet.
I don’t know what to expect from your website, so please take a moment and enlighten me as to what to expect. Was the $20 donation too small, or did I submit a difficult question, or are you off on a trip? Please advise & enlighten.
Thank you,

Hi Ray,
First we want to thank you for your generous contribution.  We also apologize for our delay and your resulting confusion.  We have a very small staff (one person who makes the identifications, formats the images and posts the letters and images to the site, and another person who manages the logistics and technical problems of the website), so we are only able to respond to a fraction of the inquiries we receive.  Though contributing a donation does not ensure that we will be able to respond to a question, we felt guilty that you were given that impression, and we tracked down your original submission in our inbox.  To respond to your question, we try to post interesting or unusual letters or photos, or submissions that might have a general timely relevance and we also directly email that response to the querant.  Other letters just get a brief identification email response, but the majority of letters are unanswered.  Your household intruder is a Household Casebearer, Phereoeca uterella.  BugGuide has much information, including:  “Habitat  Larval cases can be found on wool rugs and wool carpets, hanging on curtains, or under buildings, hanging from subflooring, joists, sills and foundations; also found on exterior of buildings in shaded places, under farm sheds, under lawn furniture, on stored farm machinery, and on tree trunks
Food  larvae feed on old spider webs; may also eat woolen goods of all kinds if the opportunity arises
Remarks  The larval case is silk-lined inside and open at both ends. The case is constructed by the earliest larval stage (1st instar) before it hatches, and is enlarged by each successive instar. In constructing the case, the larva secretes silk to build an arch attached at both ends to the substrate. Very small particles of sand, soil, iron rust, insect droppings, arthropod remains, hairs and other fibers are added on the outside. The inside of the arch is lined exclusively by silk, and is gradually extended to form a tunnel, while the larva stays inside. The tunnel is closed beneath by the larva to form a tube free from the substrate, and open at both ends. After the first case is completed, the larva starts moving around, pulling its case behind. With each molt, the larva enlarges its case. Later cases are flattened and widest in the middle, allowing the larva to turn around inside.
[from Featured Creatures, U. of Florida].
”  Again, thanks for your generous contribution.

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What's That Bug? does not endorse extermination

21 Responses to Household Casebearer

  1. Caz says:

    Oh my goodness these are ALL OVER my house and my mom and I had no idea what they were! They just looked like dried mud/dirt but then we saw one move and It was crazy! I thought I was seeing things for the longest time. Thanks guys! 🙂

  2. fransis says:

    I found one in my shower. Soooo nasty. Are they dangerous????? Or dirty like rats and roaches?????

  3. jorge montes says:

    I found some in my attic..should I be worried

  4. jorge montes says:

    Thanks ..do they cause any health problems, ,and what steps should I take to get rid of then…or can I dp ot my self…or only a exterminator

  5. fransis says:

    Thanks for the 411 bugman☺

  6. Bea says:

    Pl ease anyone – give information on how to kill these things! I pick up at least a dozen a day. Using my air conditioning all the time – humidity low and house has been thoroughly sanitized. Still have these monsters! Please help!

  7. stan says:

    yeah…I am looking on how to contain these devils

  8. ginger says:

    I’ve lived in Jacksonville, FL and Tampa, FL and have only seen them in Tampa. They love hanging out on walls. They aren’t dangerous. I usually just pick it up and put it outside.

  9. Lew says:

    Thanks for the info. I ‘ve seen these things on the walls of some offices I’ve been to in the Tampa area, and now I have noticed them in my house. Not really a problem, but unwanted and would appreciate suggestions on how to control them.

    • Bev says:

      I found these in my bathroom (Florida). I understand they like humidity and dog hair! I have 4 dogs. I flush them down the toilet!

  10. Candice says:

    I live in the Port Richey area in Florida and I have been finding these things for about 4mos now. Not having any idea what they were I honestly thought it was just a piece of fuz/dirt until the lil worm stuck it’s head out and stated moving. They are always hanging from my ceiling and walls no matter how many times I clean them up they always come back! Grrrrr!

  11. Marianthi says:

    If these larvae are cleaning up old spider webs and possibly dog hair (I’m unsure if the latter has been substantiated), then I’m happy to leave them be. I came to this site to learn what benefits they might bring to my home since with so many little creepy crawlies that is often the *case* (no pun intended). I liked the comment made by Ginger in this thread-she simply puts them outside when she comes across them. Seems most folks are interested in learning how to exterminate them! We’ve no wool clothing, upholstery, etc in the home, so I’m happy to leave them be. Old web, and ESPECIALLY dog HAIR consumption is a welcome activity in our Los Angeles home (we’re just blocks from the beach, hence more humidity here, I suppose)!

  12. Tony says:

    I have these on the walls of my shower in Thailand. I thought they were pretty cool and I assumed they were just eating the microscopic algae. I have been letting them clean the walls and just watching them. I guess I’ll need to clean them up before they hatch.

  13. Laurie says:

    I have been living in this house over 10 years and have not ever seen these until now. Please, How do I keep them from entering home?

  14. joycelyne says:

    well, i always find them at my home… honestly i do hate them and always spray perfume on them it kills them.

  15. Mary says:

    We live in Hobe Sound, FL, and have had these for about 5 years now. They seem to be worse in the summer even though the AC is on all the time that time of year. We were told they are called case bugs. I clean the house very thoroughly each week, but I find at least a dozen of them every night on my “hunt”! I drop them in the trash as I don’t like killing any type of living things, but they are definitely creepy. We saw that they like wool to make their casings out of, and deducted that they came into the house when we bought 2 new wools rugs about the time we started seeing them! Regardless of the fact that I get rid of every one that I can find daily, They just keep coming back 😩😬

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