Seasonal Development of Plant Bugs (Heteroptera, Miridae): Subfamily Mirinae, Tribe Stenodemini.

The seasonal adaptations of 8 better studied species belonging to 4 genera of the tribe Stenodemini are analyzed. A univoltine seasonal cycle with obligate diapause is characteristic of four studied species: Stenodema calcarata, S. laevigata, Leptopterna dolabrata, and L. ferrugata. Species of the genus Stenodema have winter adult diapause, whereas both species of the genus Leptopterna overwinter at the egg stage. In the remaining four species (Notostira elongata, N. erratica, Trigonotylus caelestialium, and T. tenuis) the seasonal cycle is multivoltine; in different climatic zones these species can complete from 1 to 5 generations per year, depending on the climatic conditions, and overwinter in the state of adult (Notostira spp.) or embryonic (Trigonotylus spp.) diapause. Induction of winter diapause is controlled by the photoperiodic response, which is well studied in species of the genus Trigonotylus. Under long-day conditions females lay non-diapausing (i.e., directly developing) eggs, whereas under short-day conditions they produce diapausing eggs. Cases of wing and color polymorphism are known in Stenodemini. For instance, high temperature and crowding during development of older nymphs (IV and V instars) of L. dolabrata were shown to promote the appearance of long-winged females, whereas short-winged females usually predominate in the wild; males of this species are always long-winged. Body color polymorphism in species with a univoltine seasonal cycle (Stenodema spp.) appears as the body color change of the overwintering individuals from russet-brown in autumn to bright green in spring. In multivoltine species (e.g., Notostira elongata), alternative color forms are associated with different generations: adults of the summer generation have a bright grassy body color while females of the overwintering generation are russet-brown; males do not overwinter. The example of Trigonotylus caelestialium convincingly demonstrates that the nutritional factor can have an independent value in the induction of diapause. The ability of females to produce simultaneously directly developing and diapausing eggs in the middle of summer, at high temperatures and a long day, may be considered an adaptive strategy allowing at least a part of the future offspring to survive under the conditions of unstable food supply. In general, a review of data on the seasonal development of true bugs of the tribe Stenodemini, as well as of the previously studied tribe Mirini, indicates poor knowledge of even the economically important species of plant bugs (Miridae). These data provide only a general view of the seasonal adaptations and annual cycles characteristic of species of the subfamily Mirinae. [ABSTRACT FROM AUTHOR]