Although related to insects, mites are not insects but members of the arachnid class along with spiders and ticks. The spider mites, also called webspinning mites, are the most common mite pests and among the most ubiquitous of all pests in the garden and farm. Most common ones are closely related species in the Tetranychus genus and cannot be reliably distinguished in the field. However, there is little need to do so since their damage, biology, and management are virtually the same. The presence of webbing is an easy way to distinguish them from all other types of mites.
Adults have eight legs and an oval body, with two red eyespots near the head end of the body.
Females usually have a large, dark blotch on each side of the body and numerous bristles covering the legs and body. In some parts of California, spider mites may feed and reproduce all year on plants that retain their green leaves through the winter. They begin feeding and laying eggs when warm weather returns in spring. Spider mites reproduce rapidly in hot weather and commonly become numerous in June through September. If temperature and food supplies are favorable, a generation can be completed in less than a week.