Scanning electron micrograph of a springtail. Springtails are primitive hexapods, classed as Collembola. They evolved 400 million years ago. The picture shows the simple eyes on either side of the (0.2mm wide) head, each consisting of five ocelli. These are a primitive feature, as are the short club-like antennae, picture top. Springtails are one of the most numerous animals on Earth; a hectare of meadowland may contain 500 million individuals in the top 25cm of soil. They play an important role in the decomposition of organic materials, by fragmenting leaf litter, and consuming plant and animal remains, fungal hyphae and bacteria. There are over 3500 species of springtail. A small number are agricultural pests; however, many more transport spores of mycorrhizal fungi on their rough integument. Springtails are undoubtedly a beneficial - indeed, essential - part of the soil environment.