Sexton Beetles

2007 June 16

Aaahh! Zombie Mouse!

OK, so on Wednesday, June 13[1], there was some stuff I had to haul out of the basement. The basement has one of those outdoor cellar entrances, with a slanting hatchway covering a set of concrete steps leading down. Since this was the best way to haul out bulky things, I opened up the lid . . . and saw . . . a dead mouse laying on the stairs [2]. Ok, kind of nasty, but not too bad, except . . . then . . . it started to move. Not just a little motion, it hopped up, rolled over, and fell down to the next step! Gah!

And then, the cause became obvious. These two large [3] beetles disengaged themselves from the corpse and scurried off.


Well, that explained everything. Not a zombie. These are “sexton beetles”, genus Nicrophorus. They kind of separated after this so I couldn’t get both of them in one picture after that, but one of them eventually stood still long enough to get some fairly clear pictures[4].


They are most likely Nicrophorus orbicollus, although they might be Nicrophorus sayi[5], or maybe some other similar species that hasn’t gotten into “Bug Guide” yet.

Sexton beetles are a big part of the reason why you will rarely find small animal corpses lying around in the woods. As I understand it,[7] this is what normally happens: (1) Some small animal (bird, mouse, chipmunk, etc.) dies. (2) That night, a pair of these beetles flies in, and proceed to dig underneath it to bury it (if necessary, they move it to soft soil first, by crawling underneath and heaving with their legs). (3) Once it is buried, and protected from other carrion-feeding insects, they lay their eggs on the corpse, and then dig a little burrow next to it where they raise their young, feeding them bits of the dead body.

The thing is, I found them in an anomalous situation. The basement steps were obviously something that they weren’t going to be able to bury the corpse in. So, what they had done is find a hole at the side of the steps that they could turn into a burrow, and as near as I could tell they were cutting up the mouse and carrying it off into the burrow piece by piece. They had largely hollowed out the mouse, leaving nothing much other than skin, bones, and hair for the other carrion-feeders to get at.

So, there you have it. This was actually not one of the arthropods I was expecting to find in the house, but hey, when the opportunity presents itself. . .

[1] Coincidentally, this was the day of “blog like it’s the end of the world”, where everybody was supposed to have a blog entry as if it was the Zombie Apocalypse. Ideally, I should have posted this then, but it didn’t occur to me that it would have been oddly appropriate until later.

[2] It was not merely dead, but really most sincerely dead. Flies and everything[6].

[3] Each one was over an inch long. [8]

[4] I suppose I could have grabbed one to photograph more carefully in better light, but come on! They had just crawled out of a putrescent mouse carcass! Maybe if I had some tongs . . .

[5] Once again, the ghost of Thomas Say waves “hello”.

[6] I believe I mentioned earlier that our basement is kind of nasty. What, you thought I was kidding?

[7] When I was a kid, my parents had this book of natural history essays that had been collected by (I think) Readers’ Digest, and one of them was a fairly involved description of how sexton beetles do their work.

[8] It occurs to me that this is a mechanism for zombification that hasn’t really been addressed in any horror movies yet: there have been supernatural zombies, and technological zombies, and zombies that were just people infected with some disease that destroys their minds, but I don’t think there have been any where the zombies were being animated by carrion beetles inside, “pulling the strings” so to speak. They could be animating the bodies to generate more fresh corpses for their larvae to feed on. Charming thought.

7 Responses
  1. Mike Edwards permalink
    November 8, 2007

    In response to #8, Men In Black. 🙂

  2. November 9, 2007

    Good point, I’d forgotten about that.

  3. Emilius permalink
    November 12, 2007

    Also in response to [8];

    White Wolf (the company that makes the horror role-playing game World of Darkness) has invented the Azlu; spider-like supernatural creatures that have a tendency to eat their way into living human beings, eat their brains and start tugging at nerves to control the corpse. After that, they eventually burst out of their mobile human cocoon as monstrous human-spider hybrids… Creepy AND gross.

  4. Bobby permalink
    July 9, 2010

    I just found your blog last night. Very fun stuff! I’ll never forget the time I found a mouse similar to the one you subscribed. Interesting and, yes, very, very creepy. Keep on writing and I’ll keep on reading!

  5. July 9, 2010

    Thanks, Bobby. There are a lot of different things that come to carrion, and I’ve toyed with the idea of just leaving out a piece of raw meat for a while to see what comes to it. Only problem with that plan is our dog . . .

  6. Chester permalink
    June 5, 2012

    These bugs are so sick! I keep finding them in my house, my wife is a clean freak cleaning all the time so I don’t know what they are doing inside my home! The walls in my house are hollow and sometimes mice live and die inside the walls. I hope I find out why they keep getting in because the one I removed last night stunk like a dead animal I found it on top of an air cleaner he couldn’t get out. Every year it is a new bug type in my house, I burn wood so it might be from the basement somewhere. Last year we had cockroaches, we live in wisconsin but there are woodland cockroaches living in dead trees.

  7. June 5, 2012

    Chester: If these are actually what you have in your house, then you must have dead animals in your walls. I’m not sure what you can do about it other than trying to plug the holes that the mice use to get into the walls.

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