Annuals, which typically dominate in early-successional habitats, are characterized by a faster relative growth rate than perennials and, therefore, a short exposure time, so that they are a spatiotemporally unpredictable resource for insects. Furthermore, the more widely distributed and abundant a plant is, the more insects it should encounter in its evolutionary history. Plant height is usually a surrogate for the complexity of the plant architecture and, generally, a well-known predictor of plant-insect ratios. Annuals have impoverished communities and both shoot length and abundance are positively correlated with insect diversity. The number of endophagous insect species associated with grass species can be predicted by (1) the annual-perennial dichotomy (annuals, in contrast to perennials, support almost no endophagous insects) (2) the mean shoot length and (3) the abundance of the host plant. The endophagous, mostly stem-boring herbivores belong primarily to the the Diptera (mainly Cecidomyiidae, Chloropidae, Agromyzidae), Hymenoptera (Cephidae, Eurytomidae), Lepidoptera (mainly Pyralidae, Noctuidae), Coleoptera (mainly Cerambycidae, Mordellidae, Chrysomelidae), and mites (Acari). Sap-feeders on grasses are Homoptera ( Auchenorrhyncha, Sternorrhyncha, Pseudococcidae), Heteroptera (mainly Miridae), and Thysanoptera. Specialization on grasses appears to be particularly important in grasshoppers, and their abundance in grasslands is high. Of the specialized grass chewers in Great Britain <2% are Coleoptera, 6% Lepidoptera, 6% Hymenoptera, and 41% Orthoptera (the grasshoppers). Grass foliage-chewing insects belong primarily to the Orthoptera, Lepidoptera, Coleoptera (mainly Chrysomelidae and Curculionidae), Hymenoptera (Tenthredinidae), and Phasmida. Which insect species attack grasses, and what are the typical plants of grasslands? Ectophages, which feed externally on leaf tissue by chewing, scraping, or sucking, are distinct from endophytic feeders, which include leafminers, gallers, and borers. The ways in which insect communities of grasslands are influenced will be the subject of the remainder of this article. Termites and ants are dominant groups in tropical and subtropical grasslands, some surface-dwelling predatory arachnids such as scorpions and solifugids are restricted to warm, arid soils, and cold tolerance limits the range of many species in arctic and antarctic conditions. Tropical grasslands and tundra tend to be somewhere in-between. Per square meter), whereas arid and semiarid steppe and desert soils, dominated by microfauna such as protozoans and nematodes, may have a biomass of only 1 g/m2. Chalk-rich temperate grasslands with abundant earthworm populations tend to support the highest faunal biomass (often >100 g fresh mass In contrast, tropical grasslands may contain over 200 plant species. Plant species richness, which determines much of the insect diversity, may be only 10 to 15 species in intensively managed and highly fertilized grasslands, but 50 to 70 in extensively managed and low-input temperate grasslands. ![]() Some marked differences are apparent between the plant-insect communities of temperate and tropical habitats. ![]() Plant and insect communities of grasslands greatly differ depending on climate, soil type, and management practices. Further features of grassland-specific insect communities include the dominance of species adapted to feed on grasses. Similarly, the litter layer of forests is larger and more heterogeneous, with a correspondingly richer decomposer community. ![]() Compared to forests, the structural complexity of the grassland vegetation is obviously simpler, so that the insect diversity is reduced. One temperate old-field grassland may be habitat for more than 1500 insect species, whereas cereal fields, which are monocultures of annual grasses, may contain 900 species. Grasslands are habitats for many insects and may harbor an extraordinarily species-rich community.
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