Ecologists hold two views about the role of herbivory in ecosystem dynamics. First, from a food web perspective in population͞community ecology, consumption by herbivores reduces plant abundance. Second, from a nutrient cycling perspective in ecosystem ecology, herbivory sometimes slows down cycling, which decreases plant abundance, but at other times speeds up cycling, which possibly increases plant abundance. The nutrient cycling perspective on herbivory has been experimentally addressed more thoroughly in aquatic systems than in terrestrial systems. We experimentally examined how grasshoppers influence nutrient cycling and, thereby, plant abundance and plant species composition over a period of 5 years. We examined how grasshoppers influence nutrient (nitrogen) cycling (i) by their excrement, (ii) by changing the abundance of and the decomposition rate of plant litter, and (iii) by both. Grasshoppers may speed up nitrogen cycling by changing the abundance and decomposition rate of plant litter, which increases total plant abundance (up to 32.9 g͞m 2 or 18%), especially, the abundance of plants that are better competitors when nitrogen is more available. However, whether grasshoppers enhance plant abundance depends on how much they consume. Consequently, ecosystems and food web perspectives are not mutually exclusive. Finally, under some conditions, grasshoppers may decrease nutrient cycling and plant abundance.

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The summer (May-September) time budgets of 14 generalist herbivore species living in the same grassland environment are presented in terms of various component activities (e.g., walking, feeding, resting, etc.). All the species exhibit a decrease in activity as average daily air temperature increases. Greater body size and variety of habitats used by a species lead to increased time spent active. Use of a greater variety of habitats may increase activity time because different habitats provide suitable thermal conditions for activity at different times of the day. Body size affects sn herbivore's thermal balance through metabolism, body surface area and thermal inertia. The time spent feeding, exclusive of time spent searching for foods, is less for large than small herbivores. This may arise because large species must spend more time walking in the search for food to satisfy their energy requirements. The observed feeding time differences for species composing a common trophic level in a single environment may help to explain their diet choice because feeding time constrains the variety of foods an herbivore can select. Diet differences, in turn, can explain the potential competition for food if food is in short supply.

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A study was conducted in western Montana to determine the impact of dtfferent predators on grasshopper populations. By placing grasshoppers of different species, sexes, _ages, and body masses on monofilament tethers in the field, rates of predation could be e~tm?-ated. These rat~s are consistent with other estimates obtained from population studtes m the same environment, but provide a far more detailed assessment of which grasshoppe~s ~r~ most vulnerable to predators and which predators are most important. Immature mdtvtduals are more vulnerable at small body sizes and adults are more vulnerable at large body sizes; this is because the principal predators on immature individuals are arthropods, and on adults, vertebrates. Male grasshoppers were 2-3 times as vulnerable as females. The subfamily Oedopodinae was more vulnerable than the Gomphocerinae or Melanop~inae. Predation rates indicate that predators are only able to impact seriously (reduce hfe expectancy below the suitable abiotic period for existence) the largest Oedo-pod~nae, making pntdation of little consequence for most grasshopper populations in this envuonment.