Why do cockroaches die on their backs?

Answer 1

There are two scenarios can think of(i.e. found) that would cause a cockroach to die on its back:

(1) Roach dies while crawling on the wall. 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.

(3) Roach dies after ingesting potent neurotoxins, e.g., Diet Coke, or some traditional bug poison like pyrethrum. 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.

Answer 2

The following discourse may shed some light on the subject.

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

Source: The Straight Dope