Phenotypic Variability of Body Coloration in the Populations of Scutellerid Bugs (Eurygaster Laporte; Heteroptera, Scutelleridae) in Cereal Crops and the Ecological Factors Responsible for It

Аннотация

Populations of shield bugs of the genus Eurygaster, which are pests of cereal crops in Europe and Asia, are characterized by pronounced modification (phenotypic) individual variability of the scutellum coloration. The scutellerid body coloration has a protective function, acting in a concealing or a disruptive way. The main ecological prerequisites for its formation include the existence of bugs under non-uniform conditions on the aboveground parts of their host plants, on the soil surface, in the upper litter and soil layers, inside secondary shelters in winter and during summer drought, and also their relations with host plants, predators, and parasites. All these factors contribute to the formation of a number of body color phenotypes with transitional forms between them and determine their spatiotemporal dynamics due to changes in the living conditions. The leading factors affecting the body color of scutellerids are the climate, especially humidity and thermal conditions during development; the soil, in particular its type and color; the vegetation features; the composition and biological characteristics of the main host plants, the prevalent entomophages, and relations between them. Within the temperate belt, the percentage of Eu. integriceps bugs with a uniformly colored dark, gray or gray-brown scutellum increases with increasing latitude and longitude, increasing precipitation in May-August, and decreasing air temperature, and also in transition from the steppe to the forest-steppe zone and from lighter chestnut soils to chernozems. Correspondingly, the percentage of bugs with a light-colored scutellum increases in the mountains and foothills of West and Central Asia. In the forest-steppe zone of Samara Province, 5 and 3 phenotypes of the scutellum color were recorded in wheat and barley agrocenoses, respectively. Bugs of the 1st phenotype were dominant in Eu. integriceps and Eu. maura populations inhabiting wheat and barley crops, while those of the 2nd and 3rd phenotypes were also quite common. The highest similarity between Eu. integriceps and Eu. maura populations in the body coloration was observed in winter and spring wheat crops.