Rhizoglyphus is a genus of mites in the family Acaridae. It has a worldwide distribution and is often associated with the bulbs, corms or tubers of plants. Description and life cycle Rhizoglyphus begin their lives as whitish, ellipsoidal eggs that are 0.12 mm long. These hatch into larvae, which are oval, white and have three pairs of legs. Larvae are 0.15-0.2 mm long on hatching and grow to 0.25 mm long. Larvae then develop into protonymphs, which are 0.4 mm long and (compared to larvae) gain an additional leg pair and two genital suckers. Under certain conditions such as high population density, protonymphs develop into deutonymphs (or hypopi), a quiescent stage that does not feed. This life stage is convex dorsally and flattened ventrally, brown in colour, 0.2-0.3 mm long, heavily sclerotised, lacks mouthparts and has a ventral sucker plate. The purpose of the deutonymph stage is to attach to insects and be carried to other bulbs (phoresis). Deutonymphs are resistant to starvation and desiccation during adverse conditions. The tritonymph stage follows the protonymph (or deutonymph). Tritonymphs are about 0.5 mm long and have three or four genital suckers. They eventually develop into adults. Adults are 0.5-0.9 mm long, shiny, white and somewhat transparent, and have reddish brown appendages. Unlike tritonymphs, they have distinct genital apertures. Some features which distinguish adult Rhizoglyphus from other mites are: 4 pairs of prodorsal setae and 12 pairs of dorsal hysterosomal setae, external vertical setae small/vestigial and situated about halfway along sides of prodorsal shield, supracoxal setae smooth, and tarsi I and II each with a proximal conical spine near bases of solenidion and famulus. The duration of the life cycle depends on Rhizoglyphus species, diet, temperature and relative humidity. At a temperature of 25 °C, it can be as short as 12.2 days for Rhizoglyphus robini and 13.9 days for R. echinopus. Adults live longer (for up to 121 days) at lower temperatures. Males tend to live twice as long as females in this genus. Host arthropods As noted previously, Rhizoglyphus deutonymphs ride on other, larger arthropods for dispersal. They have been collected from scarab beetles, weevils, various flies and fleas. Host plants Rhizoglyphus feed on a range of ornamental (e.g. Dahlia, Eucharis, Gladiolus, Hyacinthus, Iris, lily, Narcissus, orchid, tulip) and crop plants (e.g. barley, carrot, garlic, onion, potato, sweet potato, taro). While underground plant parts are most commonly attacked, the mites have