I bought DE at two different places, both containers say it is for control of insects.
Treated my chicken feed with one bag, treated several fire ant mounds with the other bag (at the recommended "dosage"). The chicken feed got a really bad infestation of weevils, which didn't seem phased by the DE. When I threw out some of the food, I found cockroaches crawling over it in the early morning hours. Captured a bunch, just to see if the DE would kill them, and they lived (disgustingly) another week before I turned them loose with the chickens (much more effective than DE!). The fireants didn't even slow down.
So I have to ask: is it possible that the effectiveness of DE is just a myth, and it really acts as a repellant and does not kill insects by "cutting up their exoskeletons"?