I replied at the other forum
glad you moved it,
they should have an entomology forum perhaps.
although there is zoology and ecology.
nematodes help to break down organic matter.
also sone kill harmful grubs that damage lawns and crop.
well, where to start, nematodes help aid in nutrient recycling, there symbiotic for a wide array of soil org (ie worms), there an indicator spp. for say such harmful things like acid rain, and they serve as phoretic/paratenic host for alot of cool parasties