MadSci Network: Zoology

Re: How does Raid affect roaches and why do they die upside down?

Date: Fri Nov 14 11:41:09 2003
Posted By: Uncle Al Schwartz, Organic synthetic chemist
Area of science: Zoology
ID: 1068705364.Zo

Most contemporary household bug killers are based upon pyrethroids - synthetic analogs of the insecticidal principle of African pyrethrum daisies (Chrysanthemum coccineum or Tanacetum coccineum).

Pyrethroids act by lethally altering the permeability of excited nerves. Their rapid metabolism in mammals and very fast knock-down in insects make them popular. Carbamate and phosphate insecticides inactivate the enzyme acetylcholinesterase at the nerve-muscle junction. They both have long term harmful effects after exposure. Pyrethroids are not especially lethal to roaches. They are more like fast-acting aesthetics. If you want to kill roaches, you need something more able. Dead things often end up on their backs because that is the equilibrium position with their center of gravity lowest to the ground. Dead fish float upside down because that places their center of gravity nearest the surface. Either way, the energy of the system is minimized. SUVs easily tip over for the same reason - too high a center of gravity. -- Uncle Al (Do something naughty to physics)

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