Roaches on their backs

I’d not had opportunity to test Cecil’s comments on roaches dying on their backs until recently. Unfortunately, the place I’ve worked since February has a major roach problem which spraying seems to have absolutely no effect on. Every day we’ve got to sweep the floor.<gag>

I haven’t yet seen one of the nasty things dead on its belly. Nor have I ever seen one crawling on the walls - or on the ceiling, which is where they’d have to be to land in some of the places they show up, according to the theory.

Methinks someone - who has a far stronger stomach than mine - might do some scientific study of roach death throes and explain why they do die on their backs. I just wish they’d die elsewhere -say in Upper Slobovia.

Welcome to the Straight Dope Message Boards, Goffs, glad to have you with us. When you start a new thread, it’s helpful to others if you provide a link to the column. In this case, Why do cockroaches die on their backs?

A related question is: why do spiders’ legs curl under their bodies when they die?

That at least has a simple answer. Arachnid limbs only have muscles that can pull the limb towards the body. Unlike mammlas there are no antagonistic muscles to pull the limb back out again. To straighten the limb spiders have to force ‘blood’ into the limb and let the hydraulic pressure straighten it.

In dead spiders the muscles contract after death, just like in humans. Because they lack any antagonistic muscles this contraction moves the limbs to the limit of the muscles, rather than just causing minor changes as it does in people. The result is a spider with all limbs drawn as close to the body as possible.

Maybe the roaches are romantics and want their last vision to be that of the heavens. Or maybe they just like creeping us out.