Referring to the table of the Habitats of Adult Animals, we see that of 37 animal phyla and subphyla all are mostly aquatic. Only 10 phyla have some terrestrial representatives. Of these 10, only 5 have representatives in dry terrestrial habitats. So when we are dealing with the terrestrial environment we are dealing with a very restricted portion of animal biodiversity. Unlike aquatic animals, terrestrial animal movement on land is primarily with legs.
Flight requires wings.
These are parasitized by roundworm, ribbonworms, etc. They are preyed upon by terrestrial flatworms, onychophorans, centipedes, scorpions, spiders, and predatory insects. They are also large enough to be food items for most amphibians, reptiles, birds, and small mammals. The smaller primary detritivores are largely preyed upon by predatory mites. The small primary detritivores are too small to be energetically productive prey items for most vertebrates.