Springtail

Class Collembola — the springtails — contains about 9,000 species worldwide and is one of the most abundant and ecologically important groups of soil arthropods on Earth. Springtails are NOT insects (the two classes diverged in the Silurian, ~420 million years ago) but are closely related; both classes are part of subphylum Hexapoda. The defining anatomical feature is the furcula — a forked spring-loaded organ on the underside of the abdomen that is held under tension by a clasp called the retinaculum. When threatened, the retinaculum releases and the furcula snaps downward, launching the animal up to 100 mm (often 100 body-lengths) in any direction. Springtails are extraordinarily abundant: typical healthy temperate soil contains over 100,000 individuals per square meter (250+ billion per acre), and they are major drivers of decomposition, fungal grazing, and soil structure. They are detritivores, fungivores, and microbivores; they do not bite, do not transmit disease, and are completely harmless. Some species in Antarctic and high-altitude habitats survive astonishing temperature extremes — Belgica antarctica and certain Cryptopygus species use glycerol and trehalose as natural antifreezes and survive -60°C. F. candida is widely used as a model organism in soil ecotoxicology testing because she reproduces parthenogenetically (no males needed, all females, all clonal) and has a short generation time.