Sf Ranch - Large - Steinernema feltiae - 500 milNemAttack Steinernema feltiae Beneficial Nematodes are live microscopic organisms (non segmented round worms) that occur naturally in soil throughout the world. The beneficial nematodes we sell are parasitic to insect pests that typically have a developing (larval or pupal) stage of life in the soil. They have been known to parasitize above ground stages of adults, nymphs and larvae. They will not harm mammals, aquatic life, birds, reptiles or