Thursday, May 24, 2012


We have an infestation of casebearer moths in our house.  What are casebearer moths, you might ask?  Well, for those of you who have followed the blog since the beginning you may remember the post Slugs, Bugs, and then Culture Shock.  For those of you who don’t remember, let me refresh your memory.  Back in October, I wrote the following:
In addition to a slug and the ants, there are these mysterious flat, almond-shaped “things” hanging on the walls and ceiling of our house.  I noticed them the day we moved in.  I thought they were just some weird, dried up, dead bug, but last night as we ate dinner, I saw one on the wall and – jeepers-creepers – it was MOVING around. I picked it up with my tweezers (after eating of course) and it turns out that they have this disgusting black tentacle thingy that pokes out that helps them mobilize… (No legs were visible!) It’s one thing to have a weird, unknown dead creature on your wall, and quite another thing to see it move around and have no idea what the heck it is.  I still have the heeby-jeebies and am on a mission to rid the house of all of them, dead or alive.

Being that I am intensely curious, I not only went on a mission to rid our house of these, but also on a mission to find out what the heck they were.  I became especially obsessed with this quest more recently when I would wake up in the middle of the night, turn on the light, and find dozens of them crawling around on my wood floor.  I was NOT okay sharing my bedroom with these creepies.

I searched on Google numerous times, having no idea even what words to choose to describe the cocoon-like creature found in every crevice.  “Weird worm in cocoon + Costa Rica.”  Or “almond-shaped cocoon” or “moth species Costa Rica”. (I knew what I was seeing was the larva form of a moth-to-be because there are always tons of little moths flying around our house, but I wanted to know MORE).  Nothing was giving me the information I was seeking, but after hours of crappily-worded searches, somehow or another I finally stumbled on a couple pages that shed some light on this mysterious intruder. 

They are called “Bagworms” or “Casebearer Moths”. This is what they look like up close:

My curiosity was finally satisfied.  I don’t know why I didn’t think of the word combination “case” + “moth” before.  My brain was stuck on “cocoon”.

Basically, what we’re seeing, and yes, what our house is infested with, is actually a caterpillar inside a protective case.  It drags the case around as it’s in its larva stage.  Eventually, it goes through the ‘pupa’ stage inside the case, creating a cocoon of sorts inside.  Crawling up a wall, it attaches itself, and according to this website, emerges as a tiny moth the next day around noon.

Below are a few excerpts from the website.  I highlighted the phrases that I found particularly interesting.  Or disturbing.  Anyway, for those of you who are curious like me, you may continue reading… and viewing my gross pictures.

Excerpts taken from:



Egg: After mating, females lay their eggs on crevices and the junction of walls and floors, cementing them on debris. Two hundred eggs may be oviposited by a single female over a period of a week, after which she dies. Eggs are soft, pale bluish, and about 0.4 mm in diameter. 
Look close and you will see a case sticking out from under the top molding.  I scraped this out with a nail. 
A partial-view of all our wood 'crevices'.  In every 'crevice' or gap between pieces of wood are several old or new casebearer moth cases.
Larva: The larva is not usually seen by most people. The case that it carries around wherever it feeds is what is immediately recognized. It can be found under spiderwebs, in bathrooms, bedrooms and garages. Cases can be found on wool rugs and wool carpets, hanging on curtains, or underneath under buildings, hanging from subflooring, joists, sills and foundations; on the exterior of buildings in shaded places, under farm sheds, under lawn furniture, on stored farm machinery and on tree trunks. 
This is underneath a shelf in Kate's closet.  The picture doesn't do justice to how many were actually hanging there.  Probably about 50.
Due to its food habits the household casebearer is a potential household pest. However, regular cleaning practices, increased use of air conditioning in houses, and reduced number of woolen goods in this part of the country, along with pesticide application in cracks and crevices for household pest control, have decreased the incidence of the household casebearer. Manual picking or vacuuming of cases and spider web removal should be enough to keep this species under control. [I am obsessed with 'manually picking' these critters out of the 'cracks and crevices' of our house.  My favorite tools to do so: a tiny screw driver and a nail.]
A pile of old cases I cleared out from just one wall yesterday.  I know... I'm weird.  But like it says, manual picking helps to keep the population down!
 So, all this to say, at least I know what they are now.  And if read all the way to the end, you probably are in agreement with me: these things are GROSS!


  1. siiiiiccckkkkk! Bless your heart digging all those out... what else are you going to do though... huh. Creepy.

  2. Oh my, we had the same kind of infestation! I saw these little packets of dirt hanging on some of our walls; I thought they were nothing but a small pile of dirt hanging for some unknown reason until my son screamed as he ran out of his room. He noticed that all the cocoons were under his sheets! In that instant, I called for help. It took them half a day to rid our house of these pests. I hope you’ve resolved this already!

    Lucile Lynch

  3. I was amazed to come across ur blog, explaining ur discovery of the household casebearer. I have the exact same story. I live in Johannesburg, South Africa. As we moved into our home 4 years ago I noticed these strange grey dried out like insects on the walls & sometimes the floors. Thought they were odd but didn't think much of it until a day ago when I notice a black worm like head poking out of the one end. I freaked out & obsessed about manually picking them with paper towels & throwing them in the bin. I was so grossed out I could not stop obsessing about what they could be, what caused them & how to get rid of & prevent them. I too just had no clue how to describe it when googling & eventually though of 'worm in soft flat shell'. I also came across ur blog & thought had to respond since I had same experience all the way across the ocean. Thx for ur help on extreme detail. My husband & I are going to get our kids & cat out the house to have it fumigated.

  4. Good thing I stumbled on your blog. You’ve shared valuable information that can help your readers in spotting those pests. It’s hard to locate them, but these signs of infestations will help you remove them from their breeding places. Years have passed already, and I hope your infestation problems are already solved. :)

    Christian Lewis @ BeelinePestControl

  5. We've got the same little critter in our San Jose Costa Rica condo.. I would see them once in a while on the walls and I picked one off the wall and tore it apart and found a little Caterpillar like grub inside. They have not been much of a bother. But since moving here I've seen them in other places, garage, office and church.

  6. Its not that gross for me, just weird, and annoying. When I first saw them in my rented room, I thought they were pupa of some insects, so I kept an eye on them (I like to observe these sort of things). Until one day, I saw one crawling around then I saw this black eerie worm protruding from the inside. I searched for "worms that carry a bag", browse through the images then found the identity of this creepy creature. Since they seemed quite harmless to me (I dont have silk/woolen products here), maybe I will collect these things as pets. Hehe

  7. dear Joe & Jenny.. Appreciate your etailed documentation of these pests..we have almost 10 everyday which i spot & destroy..
    Thankfully reassured that their not much to worry about..would post details if i find a permanent solutions..Right now its wet wipes..& exploring crannies & crevices.. regards

  8. dear Joe & Jenny.. Appreciate your etailed documentation of these pests..we have almost 10 everyday which i spot & destroy..
    Thankfully reassured that their not much to worry about..would post details if i find a permanent solutions..Right now its wet wipes..& exploring crannies & crevices.. regards

  9. dear Joe & Jenny.. Appreciate your etailed documentation of these pests..we have almost 10 everyday which i spot & destroy..
    Thankfully reassured that their not much to worry about..would post details if i find a permanent solutions..Right now its wet wipes..& exploring crannies & crevices.. regards

  10. Goodday! I live in Pretoria South Africa, and discovered these weird packets attached to the walls and also a few hanging from the ceiling. I moved into this house 4 years ago. This is the first time a see these thingings on return from vacation. I also found some on the outside walls, but only were the area is under roof and where there are ceilings. How should I treat this pest? Can I use room fogger and target area by area or should I call in a pest controle company? I'm working from home and have pets, difficult to evacuate the house for a period. Can it also be between the roof and ceiling? Can it course any damage there?
    I also experience a problem with Beatles, black with white markings, drilling into the wooden beams supporting my tiled roof. I have painted the wood several times with....., but it keeps on returning. I have called it a pest controle company, but they did not have any solution for the problem. According to them and my research it is wood bore worms, although the beatles are mainly what is visible. I'm worried about my roof structure, because I'm unsure how deep these iworms/larvae can drill in the wood.
    Anyone that can PLEASE give me advice?


  11. هل تعبت من الحشرات المنزليه وخاصة الفئران والصاصير؟ نحن نوفر لك افضل خدمات مكافحة الحشرات والقضاء عليها بما يوفر لك راحت البال منها
    شركة مكافحة الفئران بالرياض
    شركة رش مبيدات بالخرج
    شركة مكافحة حشرات بالخرج

  12. I found this bug this in my house too. However, I live in Southern California where it is dry and arid. But this summer has been very humid. As a life long resident, this is the first time I've seen one of these! Yikes! I hope I don't have more, but. Ow I know what to look for
    .. thank you