why do roaches turn on their backs when they die?

Answer 1

not all of them do, but these shelled creatures are top heavy and lose their balance if they are not able to function but their legs are still extended. Also their internal circulation is not through "pipes" but through "troughs", so to speak. If there is a toxin irritating the system, turning over empties the system (within the larger shell). If they still have the resources to turn back over, the insect may have diluted the poison enough to continue on.

Answer 2

The Straight Dope covered this a few years back (reference 1).

Dear Cecil:

While working part-time in the food service at USC, I had the opportunity to see thousands of dead cockroaches. One thing about these roaches intrigues me: why did they all die on their backs? Is it programmed into their tiny little genes, or do they do it just to bug us? --Leslie, University of Southern California, Los Angeles

Dear Leslie:

Frankly, if I saw thousands of dead cockroaches at the food service where I went to school, I'd have other things on my mind than why they all died on their backs. Besides, they don't always die that way--basically it depends on how the little scumbags happen to meet their Maker. I've been discussing the subject with the crack bug scientists at some of the nation's leading institutions of higher learning, and we've formulated the following Roach Mortality Scenarios, which represent a major step forward in our understanding of roach postmortem positioning:

(1) Roach has heart attack while crawling on the wall. OK, so maybe roaches don't have heart attacks. Just suppose the roach croaks somehow and tumbles earthward. The aerodynamics of the roach corpse (smooth on the back, or wing side; irregular on the front, or leg side) are such that the critter will tend to land on its back. Or so goes the theory. Admittedly the study of bug airfoil characteristics is not as advanced as it might be.

(2) Roach desiccates, i.e., dries out, after the manner of Gloria Vanderbilt. This is what happens when you use Cecil's Guaranteed Roach Assassination Technique, described elsewhere in this archive. The roach saunters carelessly through the lethal borax crystals, causing him to lose precious bodily fluids and eventually die. Since this process is gradual, it may happen that the roach simply conks out and dies on its belly.

(3) Roach dies after ingesting potent neurotoxins, e.g., Diet Coke, some traditional bug poison like pyrethrum, or the food served at USC cafeterias. Neurotoxins cause the roach to twitch itself to death, in the course of which it will frequently kick over on its back, there to flail helplessly until the end comes. No doubt this accounts for the supine position of the deceased cockroaches you observed.

One unresolved issue. Having seen thousands of dead roaches, did it occur to you to avail yourself of, say, a broom?

--CECIL ADAMS

Answer 3

The game's over and there's no running from it.

Answer 4

GREAT question... That's hilarious. All beetles do that and I've never thought to wonder why!

Answer 5

Why do you lay your corps facing up in the casket?

Answer 6

So they can turn their toes up.

Answer 7

So you can kiss their asses