Spider Mite

Spider mites are tiny plant-feeding arachnids in the family Tetranychidae, with the two-spotted spider mite, Tetranychus urticae, among the most widespread and economically significant species worldwide. Despite the name, they are not true spiders but close relatives, sharing the eight-legged body plan of adult arachnids along with the ability to produce fine silk.

They are found wherever their host plants grow, from outdoor gardens and field crops to greenhouses and indoor houseplants, and are considered a common pest of ornamental and agricultural plants due to the visible damage their feeding causes to foliage.

• Tiny oval body, typically pale yellow-green, though color can shift to orange or reddish, especially in cooler weather
• Two-spotted spider mite shows a pair of darker spots visible on the back through a hand lens
• Fine silk webbing often visible across heavily infested leaves and stems
• Eight legs in nymphs and adults, six in the newly hatched larva
• Best detected by tapping or shaking foliage over a sheet of white paper and watching for tiny moving specks, since individuals are barely visible to the naked eye

Spider mites are found virtually worldwide wherever their many host plants grow, including gardens, greenhouses, field crops, orchards, and indoor houseplants. They favor the undersides of leaves and thrive especially in hot, dry conditions, which speed up their reproduction.

Spider mites feed by piercing individual plant cells with needle-like mouthparts and withdrawing the cell contents, which causes the fine yellow or bronze stippling often seen on infested leaves. Heavy infestations produce visible fine silk webbing over leaves and stems, used for shelter and dispersal. Because of the plant damage they cause, they are widely regarded as a garden and agricultural pest species; natural predators such as predatory mites, lacewings, and lady beetles help keep populations in check in many ecosystems.

The life cycle proceeds from egg to a six-legged larva, then through two eight-legged nymphal stages (protonymph and deutonymph), and finally to the adult. Under warm conditions this cycle can be completed in as little as one to three weeks, allowing many overlapping generations across a single growing season. In temperate climates, fertilized adult females typically overwinter in bark crevices or soil litter before becoming active again in spring.