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Old 08-06-2015, 04:10 PM
cahutchins is offline
Join Date: May 2014
Posts: 8

Why do cockroaches die on their backs? Hydraulics and gravity!

Regarding "Why do cockroaches die on their backs?" I have a simple theory, and I'm prepared to demonstrate it with the most convincing research tool available — a poorly drawn diagram.

So we know that insect legs operate with a sort of biological hydraulics system, where circulating body fluids are used to extend leg joints. As we all know, when an insect or spider dies, its legs tend to curl up underneath them.

I propose that in the process of a roach (or other arthropod pest) giving up the ghost, their hydraulic system starts to fail, and their limbs begin to curl up. As the limbs curl, the bug's natural center of balance shifts until they simply fall over. I include here a link to a (very) crude drawing that may or may not illustrate what I think is happening.

If this mechanic is really what happens, it easily explains why you usually find dead bugs laying on their backs — no need for wild theories like neurotoxin spasms or skydiving accidents. It doesn't matter what kills 'em, it's hydraulics and gravity that flips 'em.

Last edited by cahutchins; 08-06-2015 at 04:12 PM.
Old 08-06-2015, 04:16 PM
TriPolar is offline
Join Date: Oct 2007
Location: rhode island
Posts: 41,169
You know, I thought I found the quirkiest hobby/pastime with the belt guy, but here you go and make it a run for the money.
Old 08-06-2015, 04:23 PM
Canadjun is offline
Join Date: Oct 2003
Location: Alberta Canada
Posts: 4,482
But why would the hydraulics fail so disproportionately on one side to make the critter roll over?
Old 08-06-2015, 04:31 PM
cahutchins is offline
Join Date: May 2014
Posts: 8
But why would the hydraulics fail so disproportionately on one side to make the critter roll over?
It wouldn't matter if the legs failed disproportionately or evenly, what matters is that the dying/dead bug would suddenly be balanced like an inverted pyramid. the way the bug is shaped means once it starts tipping, it's going to keep rolling until it gets on its relatively flat back, and there it lies.

Am I explaining this sufficiently? Because it makes perfect sense in my mind's eye, but I'm not positive that i'm making sense to anyone else, hence the bad drawing.
Old 08-06-2015, 04:53 PM
Senegoid is offline
Join Date: Sep 2011
Location: Sunny California
Posts: 14,937
My theory: Dying bugs, like other dying critters, don't usually just drop dead instantly. Dying is more often a slow, torturous, gruesome process, attended with much writhing, kicking, and flailing. (Much as we all find comfort in the fantasy that Granny died peacefully in her sleep, I don't think it usually actually happens that way.) Thus, the common phrase "still kicking".

If a bug kicks and writhes as it dies, there would be a fair chance that at some point it more-or-less randomly flops over on its back. And once there, since the bug is just randomly kicking (rather than purposefully kicking), and its legs are up in the air, it can't turn itself over again.
Old 08-06-2015, 05:10 PM
watchwolf49 is offline
Join Date: Dec 2009
Location: State of Jefferson
Posts: 8,499
(4) Roach dies after severe vertical force redistribution. This is the "flatter than a pancake" death scenario often overlooked as the cockroach isn't normally recognizable afterwards, depending on how much of the cockroach is retained on the redistribution mechanism (i.e. your shoe).


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