How long will it take a dead bug to decay?

Written by Joe Ballenger

We got this question in our Facebook inbox, and it was one of those questions which kind of nerd-sniped me.

Hello, so I have a rather odd question. I understand bugs have exoskeletons. So the decaying process can take a long time. I have a gnat fly who is now dead and stuck inside me television. The TV gets hot so, you think it would help the process. So what will happen to this gnat. Will it decay or will he be inside my TV forever. Thanks!


Pinned beetles. Image Credit: Nancy Miorelli

Even though this is a fly stuck in a TV, this brings up a really important question that I had never considered before today.

We currently live in a world where much of our data has a finite lifespan. Information stored on digital media will decay after awhile, and will eventually disappear after a few decades. Eventually the raw data I generated last week will no longer be around, no matter how important it ends up being.

Taxonomists, the scientists who catalog new species, store their data in a physical manner. Everything we know about insects are contained in collections, like the pinned beetles above. To document insects, we need physical specimens, and these are preserved by sticking pins through them and keeping them in the optimal environment which prevents decay…kind of like the example of the fly in the TV.

So how long will an insect last, if kept in the optimal conditions?

Bugs Don’t Really Decay…

The reason this nerd-sniped me was because I simply have no idea how long insect bodies actually last under these conditions, and I’m not sure anyone does.


Image Credit: Randall Munroe, via XKCD. License info: CC BY NC 2.5

A lot of insects will decay fairly quickly, so long as they’re soft-bodied and exposed to the environment. I do a lot of experiments in potted plants, and when bugs like Aphids die, you’re simply not going to find them in the dirt after a few hours. They’re gone.

However, this isn’t an aphid…and it’s not in dirt. It’s a fly in an environment where it was quickly dried out, and is in an environment which won’t really allow things to decay.

So this brings up a really good question…how long does it take an insect to decay?

We’ve got a fairly decent fossil record, thanks to the fact bugs have a really tough exoskeleton. It’s not as great as we’d like it to be, but we’ve still got enough to figure out the evolutionary history of many insect lineages through fossil histories. Lice have also been found on combs dating back nearly two thousand years.

Unfortunately, I wasn’t able to figure out how old the oldest non-fossil insects are. The Guiness Book of World Records lists the oldest known pinned insect specimen from a natural history bug collection is about 300 years old, which is far younger than the lice found on mummies.

Given the proper preservation conditions, dried insects can stick around for quite some time…possibly thousands of years. This is very good news for bug collections, which house really important records of things like crop pests and species distributions.

Unfortunately, for the person who submitted this question, it also means that fly will be stuck in his TV forever.

Author’s Note:

As we’ve announced on Facebook, we’re going through a backlog of emails. It’s the height of field season, and between our jobs and everything else…we’ve gotten a tad bit behind. It may take us a few weeks to get back to your emails, but we are currently going through the backlog.

Thanks for your patience…it means a lot to us. šŸ™‚

About Polistes fuscatus

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1 Response to How long will it take a dead bug to decay?

  1. Paul says:

    While reading this article, I was reminded of a dead spider that had been trapped inside a news board at my elementary school. It was a huntsman, and about as big as my hand (I live in Australia).

    By the looks of it, the spider had been seen by someone changing the articles in the case. I come to this conclusion because it was missing two legs that I assume were taken off when the sliding glass window was closed in panic at the sight of it.

    I first noticed this spider body in my first year at that school. Six years later, it was still there and looked exactly the same.
    I went back a couple of years ago, and it was still there without a single detail missing. That’s at least 12 years.

    I have to assume the caretaker of that particular news board is as much of an arachnophobe as I am.


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