Tiny Earth Dwellers: Unveiling the World of Soil Invertebrates

1. Soil Invertebrates

2. Protura • 0.5 – 1.5 mm • ca. 500 species worldwide • no eyes or antenna • feed on organic matter and fungal spores • inhabit moist soils and humus • temperate deciduous forests

3. Diplura • ca. 5 mm • ca. 800 species worldwide • no eyes • inhabit moist soils, leaf litter, humus • most are predators; also feed on organic • matter • common in grassy and wooded habitats

4. Collembola (springtails) • < 6 mm • ca. 6,000 species worldwide • > 300 million individuals/acre have been found in grasslands • inhabit soils, leaf litter, fungi, decaying organic matter • feed on decaying vegetations and fungi; a few species are herbivores • and predators • common in grassy and wooded habitats

5. Bristletails and Jumping Bristletails • 7 – 15 mm • ca. 300 species worldwide • inhabit leaf litter and decaying organic matter • some species are common in buildings and feed on • starches in books, wallpaper, clothing, and paper • (silverfish) • feed on decaying organic matter, fungi, algae, some • plant material • live in grassy and wooded habitats • jumping bristletails are very common in shrubsteppe

6. Isopods (Sowbugs and Pillbugs) • 1 – 2 cm • crustaceans (related to shrimp and crabs) • pillbugs roll up into a ball when disturbed • inhabit leaf litter and decaying organic • matter • feed on decaying organic matter and • fungi; some feed on plant material • breathe through gills • carry 7-200 eggs in a brood pouch

7. Centipedes • ca. 2,500 species worldwide • 1 pair of legs per body segment (15 – 177 pairs, depending on species) • first pair of legs modified into venemous fangs • found in or on soil surface in moist habitats, under bark, stones, and logs • predators (on insects, spiders, other small animals)

8. Millipedes • ca. 2.5 – 10.0 cm • ca. 80,000 species worldwide • 2 pairs of legs on most segments (30 – 375 pairs of legs, depending on • species) • found in or on soil surface in moist habitats, under bark, stones, and logs • most species feed on decaying organic matter; a few species are predators • and herbivores

9. Earwigs • ca. 1.5 – 2.5 cm • ca. 1,800 species worldwide • most have a pincer used for grooming, defense, and courtship • found in or on soil surface in moist habitats, under bark, stones, and logs • most species are scavengers or herbivores, feeding on a variety of plant • and animal matter; a few species are predators

10. Beetle larvae • White Grubs • larvae of weevils, scarab beetles, blister beetles • occur in grassy fields, crop fields, and rotten logs • feed mainly on plant roots • blister beetles are predators on grasshopper egg pods • Wireworms • larvae of click beetles • occur in grasses and crops • feed on plant roots

11. Beetle larvae • Predaceous Forms • larvae of ground beetles • live in burrows in the soil, under leaf litter, logs • occur in grassy fields, crop fields • generalist predators on other invertebrates; some • species feed on snails and slugs • Mealworms • larvae of darkling beetles • occur in grasses, stored • grains, forests • feed on live and dead • plant material

12. Fly larvae (maggots) • larvae are legless and often have indistinct heads • occur in moist habitats, leaf litter, organic matter, decaying carcasses • some feed on decaying organic matter (e.g. cranefly, moth flies, some • midges, muscid fly, blow fly, flesh fly) • some feed on plants (e.g., cranefly) • some feed on fungi (e.g., fungus gnats) • some are predators and parasites (e.g., robber fly, dance fly, blow fly, • flesh fly, tachinid fly)

13. Moth larvae (cutworms, armyworms, webworms) • larvae have well-developed head capsules with chewing mouthparts • larvae have 3 pairs of legs on the thorax and 2-5 pairs of prolegs • common in grasses and cropland • herbivores on plant roots and shoots • can occur in very high numbers (e.g., sod webworms in grasslands) • can be significant crop pests

14. Ant • ca. 9,500 described species • widely distributed in a variety of • habitats • build nests in the ground or wood • occur in very high numbers in colonies (e.g., 5,300 ants/m2 in a tropical • lowland forest in Brasil) • have castes (e.g., workers, queen, soldiers) • some species are seed-feeders (e.g., harvester ants) • some species are strict predators (e.g., army ants, fire ants) • some species omnivore, feeding on plants and animals • most species are opportunistic foragers – feeding on a variety of live and • dead plant material • “ecological engineers” – alter soils and environments

15. Pseudoscorpions • ca. 2 – 8 mm • ca. 200 species in North America • large pincer-like claws; no stinger • most species have a venom gland • found in leaf litter and under bark and stones • predators on small invertebrates (e.g., moth larvae, beetle larvae, ants, • mites) • some live under the wings of beetles and feed on mites

16. Mites • usually < 1 mm (up to 10 mm) • ca. 45,000 described species • extremely abundant in some habitats (e.g., up to 1 million per m2 of • coniferous forest litter) • found in most terrestrial and aquatic habitats • abundant in leaf litter and decaying organic matter • feed on plants, organic matter, fungi, bacteria, protozoa, and animals • influence decomposition by shredding and feeding on organic matter, • and fungi. • some are major crop pests

17. Spiders • ca. 2,500 species in North America • found in all terrestrial habitats • most have 8 eyes • have poison glands • some species spin webs • eggs often laid in silken sacs • predators on many invertebrates

18. Harvestmen (daddy longlegs) • ca. 5,000 described species worldwide • have at most 2 eyes • have no poison glands or fangs • do not produce silk • prefer moist habitats; found in forests, caves, grasslands • feed on other invertebrates, plant material, decaying organic matter, fungi

19. Earthworms • over 7,000 species worldwide • no eyes • occur in most temperate soils and many tropical soils • can have 50 – 300 earthworms/m2 of crop soil • prefer soils with abundant organic matter • feed on organic matter and plant materials in soil; obtain nutrients from • bacteria and fungi in organic matter • take soil in and deposit undigested food as “worm castes” • can produce tons of casts per acre each year • facilitate nutrient cycling, nutrient mineralization, and decomposition • can turnover the top 15 cm of soil in 10 – 20 years

20. Nematodes • typically < 1 mm • about 20,000 described species • can be very abundant (millions/m2) • many trophic forms • fungal feeders • bacteria feeders • predators on other nematodes and protozoa • omnivores (feed on a variety of organisms) • herbivores on plant roots • animal parasites • recycle nutrients by feeding on soil microbes and decomposing organic • matter