Giant Red Velvet Mite Dinothrombium sp.
Family: Trombidiidae
© nan
Kgalagadi Transfrontier Park, South Africa
Mites are arachnids in the order Acari, along with the ticks. There are over 30,000 species of mites, and perhaps thousands more to be discovered. Mites have many lifestyles: some are parasitic, some are scavengers, some are predators and still others are herbivores.
The brightly red-orange coloured adults of the genus
Dinothrombium are among the largest known mites, with some individuals of the African species exceeding 12 mm in length. The giant velvet mite is covered with a thick red coat of scarlet hair-like setae. The adults have eight legs but the young hatchlings emerge with six legs, not eight.
They are found in sandy desert areas, in soil, and in soil litter habitats around the world. Adult velvet mites spend most of their lives in subterranean burrows in a diapause-like state waiting for a specific set of ecological conditions triggered by summer rains. On desert soils, adults only emerge to the surface of the sand after heavy rain, and may only forage for a few hours per year.
These mites have a rather complex life cycle, with pre-larval and larval stages, three nymphal stages (protonymph, deutonymph, and tritonymph) and then adult males and females. The prelarvae, protonymphs, and tritonymphs are calyptostatic, meaning that they are inactive. The larvae are ectoparasitic on other arthropods. Red velvet mite larvae in the genus Dinothrombium have been found on insects in the order Orthroptera (grasshoppers), Coleoptera (beetles), Lepidoptera (moths and butterflies), and on spiders and sun spiders. The deutonymphs and adults are free-living predators of small arthropods and their eggs.
Complex mating behaviors have been described for a few species of these beautiful arachnids. The male and female mites do encircling dances, during which pair-dance signaling threads are deposited. In at least one species, the dancing pair tap each other with their first pair of legs. Sperm transfer is indirect, with the male depositing a spermatophore that is then picked up by the female. The male may deposit his sperm (spermatophore) on elevated surfaces such as twigs or stalks. One author describes these areas as love gardens. The male will deposit an intricate trail of silk leading to the sperm. The female lays her eggs in masses in the soil or sand. The number of eggs laid varies with the species. One species of
Dinothrombium (
D. tinctorium) lays 100,000 eggs.
© Richprins
SE Botswana
