Anthocoris nemoralis

Anthocoris nemoralis is a predatory bug in the family Anthocoridae. The species is native to Europe and is introduced to North America. This polyphage is a predator of aphids, spider mites and jumping plant lice (Psyllidae), and is therefore used as a biological pest control agent.

Description

Adults of the predatory bug Anthocoris nemoralis have sizes from 3 to 4 mm. The colour ranges from brown to black with white markings on the wings. Also, a distinctive feature is the reflective front wings and the black pronotum. Males and females are similar to each other.

After hatching, the nymphs are almost colorless, but soon turn yellow, orange, or brown. Almost all nymphal stages have red eyes. Nymphs grow to about 6 mm in length.

Younger nymphs have a yellowish-orange colour, and the larger ones having a yellowish to orange head and thorax and a darker coloured abdomen. The length increases to 5-6 mm.

Life cycle

Egg

The egg has an oblong shape and has a creamy white colour, and its length is 1-2 mm. These eggs are barely noticeable and are laid in young leaf tissue and on buds. The white hat is the only visible part of the egg.

Females lay eggs mainly in plants damaged by phytophages. The predator’s attraction to plants infected with pests is associated with volatile substances released by the plant when damaged by Psyllidae.

The eggs hatch after about 7 days and develop into subsequent nymph stages.

Nymph

The nymph stage lasts about 16-18 days, depending on climatic and food conditions. The first generation of larvae begins to develop, feeding on small psyllids (jumping plant lice). The eggs and larvae of the pest become victims of the entomophage.

Imago

At temperatures above 10 °C, females begin to lay eggs. The female Anthocoris nemoralis lays from 100 to 200 eggs during her life and produces 3-4 generations per year.

Anthocoris nemoralis can also hunt spiders, aphids, mites, caterpillars, butterflies and many other insects. With a high prey density, the predator kills more prey than is required for food.

The adult insect overwinters in protected areas, such as cracks in the bark, dry trees or fallen leaves.

Distribution

Anthocoris nemoralis has a West Palearctic distribution and is found from the British Isles across Western Europe East to the Caucasus and South to the Mediterranean basin. It is absent from Fennoscandia. It was introduced into Eastern Canada accidentally, and then in 1963 was introduced purposefully into British Columbia in an attempt to control pear psylla. Later it spread southwards to California where it feeds on various exotic psylla pests of ornamental plants.

Compatibility with pesticides

The entomophage has developed tolerance to certain insecticides, such as azinphos-methyl, chlorpyrifos, amitraz and thioquinox. But they remain extremely sensitive to pyrethroids.

Result

Both the nymphs and the adults of A. nemoralis are predaceous, feeding by plunging their proboscises into their insect prey and sucking out the body fluids. Adults overwinter under bark, among leaf litter or in other sheltered locations. They emerge in spring to lay their eggs in plant tissues of their host tree. In leaves, the eggs are inserted under the epidermis so that there is a bulge in the leaf surface, and only the whitish operculum at one end of the egg is visible. These soon hatch into nymphs, which feed voraciously. The whole developmental cycle takes about 15 days, and there may be up to four generations in a year.

These bugs are able to utilize a range of different trees, with a wide range of prey being targeted; the prey include aphids, spider mites, thrips, juvenile scale insects, pear psylla and the eggs of a variety of insects. The French entomologist Franck Hérard in 1986 listed it as eating twelve species of insect and five species of mite. In Europe, it is considered to be one of the most important control agents of Cacopsylla pyricola and Psylla pyri and has a density-dependent relationship with the former.