Stethorus pusillus (Herbst, 1797)

Widely referred to in the literature as S. punctillum (Weise, 1891) but now accepted under the older name of pusillus, this very efficient predator of spider mites is known under various common names such as the ’Spider Mite Destroyer’ and is widely available commercially for use under glass to combat infestations of the hugely-destructive Red Spider Mite (Tetranychus urticae C. L. Koch, 1836) which is known to attack and seriously weaken almost any plant of commercial value. It was introduced into North America in 1955 to help control citrus and avocado mites in orchards in California but failed to become established, since that time it has been unintentionally introduced on several occasions and it is now established in southern Canada and the along the west coast and the north east of the United States. It was first produced in large numbers in the 1990s following breeding experiments in the United States and is now available worldwide for use by both commercial and domestic producers. The species is native to the Palaearctic region and occurs sporadically from Western Europe to the far east of Russia, China and Japan, it is absent from warmer areas, including central and South America, Africa and the Oriental and Australasian regions although specimens are very likely to occur along with horticultural produce almost anywhere. In Europe it is widespread and sporadically common; it extends into northern parts of Scandinavia and the UK where it is occurs throughout central and south east England. In the UK it is thought to be declining but because of its small size and concealed habits may well be under-recorded. The species occurs naturally in a wide range of habitats but is more usually associated with trees and shrubs in deciduous woodland, parkland and orchards, where it is sometimes abundant on fruit trees, and it may be common in hedgerows or on shrubs such as Hawthorn (Crateagus monogyna Jacq.) or Blackthorn (Prunus spinosa L.) in grassland or wasteland etc, and occasionally on Privet (Ligustrum ovalifolium Hassk.) in domestic gardens. Adults occur year-round, they overwinter among bark or leaf litter and are active over a very long season from early spring, peaking in abundance from June until September, they breed during spring and summer and both adults and larvae predate mites although they will also take small aphids and other insects and their early stages. Under good conditions the life cycle can be short (see below) but it is not known whether there is more than a single generation each year in temperate regions.