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Eurygaster maura Linnaeus, 1758

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Eurygaster maura Linnaeus, 1758
Common names: Wheat Bug, Wheat Stink Bug [En], Punaise des céréales [Fr], Gemeine Getreidewanze [De]

Hamoir, LIEGE ● Belgium

Description: The ovoid body of imago is light brown. The ground colour and intensity of the markings are variable. Its length varies from 7 to 11 mm. Wide triangular head is bent. Easily visible tylus is limited by lamellae on cheeks. Lateral borders are straight (this is a difference from Eurygaster integriceps Put.). Wide scutum rounded at apex, covering wing and abdomen. There are black spots on abdominal segments. At first, larva has lemon color and spherical form, then becomes dark and wingless.
This species is distinguished from the slightly larger and more common E. testudinaria by the shape of the head, which lacks a slight central depression at the front and is smoothly rounded. The hind corners ('shoulders') of the pronotum are also slightly less protruding. These characters are not always reliable; genitalic examination may be necessary. Females do not show a gap between the genital plate and the previous segment (often visible in the field with a hand lens), while the male aedaegus has 2 internal spines (requires dissection).

Biology: Nymphs feed mainly on grasses between May-August, becoming adult from July. Light green eggs are also spherical, length about 1 mm. The overwintering takes place at the imago stage under fallen leaves in forests. Awakening is only observed at the end of April at temperature 18-19°C (later than that in E. integriceps). Mating takes place in May, and oviposition at the beginning of June. Bugs lay the eggs by regular rows (by 10-14 in a row) into the drop of excretion on lower side of leaves or stems. Fecundity of one female varies from 24 to 29 eggs (1.5 times less than that in E. integriceps). Embryonal development lasts 12-14 days. Insect has five larval instars. The first instar larvae do not move on plant, locating among scales of ears; older instar larvae crawl on plants, looking for food. Larvae and young bugs feed on grains. Larval stage lasts about one month.
This species is xerophilous, active at the temperatures 18-19°C. Insects essentially perish during cold damp winters with light snow covering. In spring, awakening bugs endure frequent changes of temperature and abundant precipitations. The most favourable conditions are the temperatures 24-26°C and relative humidity 60-80%. The insect endures the temperatures from 9 to 35°C without diapause.
This bug is known as agricultural pest in some regions.

Habitat: The bugs usually populate perennial cereal grasses, being able to do considerable migrations.

Distribution : Europe, Western and Middle Asia, North Africa.

References:
Interactive Agricultural Ecological Atlas of Russia and Neighbouring Countries
British Bugs