Brown Larvae in the Cupboard

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A reader wrote to us a few days ago about some “fat short brown” larvae she is finding in the her kitchen cupboards. (Yes, she did actually refer to the creatures as larvae, breaking with the common practice of calling larvae “worms,” which they technically aren’t, insofar as “worm” has a precise meaning.) The reader found the brown larvae (which might also be described as black) near a dead mouse, which had recently been killed by a trap. The reader speculated that there might be some connection between the two, a reasonable enough assumption that we will pursue below. Although the reader only found two of the larvae, she was still understandably concerned about them. She asked us what the brownish, blackish larvae are, and if she should be worried about them.

Fortunately, the reader sent a picture, which always greatly assists our worm/larvae identification efforts:

Black Larva

(The reader also included a picture of the dead mouse, but we’ll spare you.)

The creature pictured above does indeed look like a larva, and we are fairly confident we know which kind: a black soldier fly larvae, a creature we have written about many times before. We have written a thorough overview of black soldier fly larvae , and a while back a reader submitted some excellent photos of black soldier fly larvae. The creature our reader found looks a little plumper than the average BSFL (as they are often abbreviated), but its appearance and the circumstances in which it was found suggests that it is in fact a BSFL.

Since we already have articles that cover the basics of BSFL, we’ll focus on the reader’s specific situation. First, the dead mouse. Does this have something to do with the presence of these creatures in the cupboard? Yes, or it would be highly coincidental if this weren’t the case. BSFL are commonly used in composting operations, and of course compost bins are filled with food waste, some of which is from animals. So, BSFL can certainly break down the matter that composes dead animals. We have not directly heard of them consuming a dead rodent, but we see no reason why this isn’t possible. BSFL are, after all, the larvae of flies, which makes them maggots, and most of us have probably seen those disturbing pictures of thousands of maggots eating a dead animal. This is the process that is probably going on in our reader’s cupboard, but obviously (and thankfully) on a dramatically smaller scale.

Should our reader be concerned about finding BSFL in her house? Not really, and she won’t have any problems with them once she removes their food source (the dead mouse, in this case). And even if a BSFL or two lingered around the house, this isn’t cause for concern. The larvae themselves are totally harmless – they do not bite or sting, and they contain no venom. Once they mature into flies (their adult form), they are also not dangerous (or annoying: they don’t really fly around, and they can be moved easily because they aren’t scared to be touched.) We have written about the harmlessness of black soldier fly larvae before, so we encourage our reader to check out that article if she wants more information.

So, to conclude, our reader probably found black soldier fly larvae, and she has no reason to be alarmed. Of course, she’ll want to clean up her cupboard and remove the larvae she found, but that should take care of the situation.


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17 thoughts on “Brown Larvae in the Cupboard

  1. Interesting that this exact thing just happen to me. Heard the mouse trap snap. Waited till the children were to bed and went to clear and reset trap. Found two of these BSFL. They were almost as big as the mouse.

  2. I just had a mouse trapped between a feed bin and the wall of my chicken coop. I returned to the trapped mouse bb gun in hand. A moment or 2 after the fateful shot one of these bsfl crawled it’s way out of the mouses rectum.
    It’s a memory I can certainly do without!

  3. We just caught a mouse in the kitchen last night, and when I woke up this morning and went downstairs I saw one of these inching across the floor. Interesting to see the connection between these and the mice. Hopefully won’t have to deal with any more of them.

  4. That’s the freakiest thing ever, and it just happened to me! I caught a mouse in a trap in my cupboard but it wasn’t dead! I open the door and out dropped a -what I just learned is a rodent bot fly larvae pupa! WT? I’m so glad for the info. BUT SO FREAKED OUT!

  5. Found my cat with a mouse in the yard, had one of these peaking out of its hind quarters. It eventually fell out, and the mouse took off. Did some more clicking, and I’m thinking it’s more indicative of a rodent bot fly larvae, hence the connection to the mice.

  6. I also found one of these nasty worms beside a dead mouse. The mouse was just laying dead on our kitchen floor and the worm was right next to it. The mouse had a good size hole on the bottom side of it like the worm had been eating on it. Gross but glad I found this info online.

  7. So I was outside and my cat had a mouse. We have a problem with them in our trailer, so im happy to see them outside. Well my cats were kinda mean and just playing with this mouse. He could barely breathe and couldnt really move and it had a hole in its stomache. So I assumed my cat had put it there. You could barely see inside a little bit. I was about to kill it cuz I felt bad for the cats just leaving it there. And then one of these round brownish worm things started coming out of it. I thought it might have been a baby but I was mistaken. After a couple minutes of studying it. I killed it cuz I have a couple younger kids I didnt want finding it. It literally crawled out of his stomache RIGHT AFTER the mouse took his last breathe. Definitely a connection I would think.

  8. Is it just me, or does anyone else find it odd that there have been several postings of this mystery larvae just in the last few months? The mouse connection is uncanny because the “BSFL” that I found on 09/24 was accompanied by two dead mice. The thing I don’t understand is that this was literally an overnight thing because they were left in front of my living room couch and they weren’t there just 6 hours before. How did it get there that fast? My cat likes to leave me the occasional mouse present, but this fat bugger threw me for a loop! It was about as long and as fat as the tip of my pinkie finger, so it doesn’t seem to fit the size that I keep seeing online. I’m just glad I saw it before my 18 month old got a hold of it!

  9. my step dad looked down we saw the larve in the hamburger ik www he almost ate it thank god i found this website to find what it is i kinda agree its more like a parasite then a larve it was eating mouse droppings and hamburger

  10. Crazy! I cought one mouse a week ago! Then i seen a fat black larvae! Then two days ago same thing. This bug showed up!

  11. Thank you, I rescued a paralyzed bunny the other day (it was still breathing), but as I payed it in a small cardboard box, I saw one of these larvae eating through it’s armpit, then later, It came out through the neck. I ha to lay the bunny back outside because the larvae ad ended up eating it’s heart. If you see these near your small pets, I suggest you remove them.

  12. I just witnessed three of these larvae coming out of a mouse that I just killed. Absolutely disgusting. Definitely a parasitic relationship.

  13. So thankful that you posted this information. I was feeling very stressed to find one of these BSFL next to a dead mouse that was caught in a trap last night. Yeah for the internet!

  14. I found a dead mouse in a trap I set in my shed. The mouses face had been eaten away and a bsfl was half way out of its anus, as if the larvae had eaten it’s way through the mouse. I have photos but I am not sure how to share them on here. And they are pretty gruesome.

  15. I was glad to find this, as I found one of these fat short brown guys too. And it was next to a dead mouse. However, they both appeared next to my bed! The larvae was about 2 feet away from the mouse. I’m pretty sure my cat caught and killed the mouse, but how would the larvae have gotten there!?

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