They can attack a wide variety of insects and related animals: grasshoppers, crickets, cockroaches, beetles, and katydids, as well as dragonflies, caddisflies, millipedes, centipedes, spiders, crustaceans, leeches, snails, slugs and other invertebrates.Once they hatch, immature horsehair worms try to infect a host.Eggs are laid in a long, gelatinous string in fresh water.It is common to see a number of worms to be intertwined, forming a loose ball during mating.Males coil around females in pools of fresh water or damp soil.Horsehair worms mate during spring, early summer or fall.