Etri

Etri (Ixodiphagus hookeri) is a predatory mite that is used for the biological control of spider mites, especially two-spotted spider mites (Tetranychus urticae). It was first described by H.W.K. Muma in 1961.

The adult female etri is about 1 mm long and reddish brown in color. The body is oval and covered with fine hairs. There are two pairs of legs, each with five joints. The first pair of legs is shorter than the second pair and end in claws. The mouthparts are located at the end of the rostrum (beak), which protrudes from the head capsule. Etri females lay their eggs on webbing or leaves near spider mite colonies.

The larvae are pale yellow and have only three pairs of legs. They grow to about 0.5 mm long before molting into nymphs. Nymphs look like adults but are smaller and lack fully developed mouthparts. They go through two more molts before reaching adulthood, at which point they begin to reproduction themselves within 10 days if conditions are favorable (i.e., high temperature and humidity). Under laboratory conditions, etri can survive on a diet of pollen or honeydew, but they prefer to feed on spider mites when available