Animals: Ditches & Itches

Officials of Chicago's suburban Des Plaines Valley Mosquito Abatement District know the difference between a mosquito drainage ditch and a hole in the ground. Furthermore, they prefer the hole. In a century-old pestilent swamp in Palos Park one afternoon last week they blasted out a vast sump, of which they planned to make a mosquito-proof "wildlife oasis." If mosquito larvae in the abaters' sump don't watch out, the bladderwort plant will get them. If insectivorous plants don't get them, whirligig beetles, back swimmers, dragonfly nymphs and top-water minnows will. Ditches get stagnant and...