Ecological Entomology (2007), 32, 754–761 DOI: 10.1111/j.1365-2311.2007.00925.x © 2007 The Authors 754 Journal compilation © 2007 The Royal Entomological Society Introduction Variation in the chemical composition of plants often signifi- cantly affects the success of individual herbivores (Awmack & Leather, 2002) and the distribution and local abundance of herbivore populations (Mattson, 1980; White, 1993). Chemical features influencing plant quality for herbivores include water content, concentrations of secondary metabolites, and levels of nitrogen (N) and other nutrient correlates. However, there is growing awareness that the ecological relevance of variation in nutrient content depends not only on the intrinsic properties of leaves but also on the mismatch between leaf composition and the nutritional demands of herbivores (Elser et al., 2000; Fagan & Denno, 2004). Ecological stoichiometry, the study of element balance in living systems, provides a framework for linking trophic imbalances driven by variation in food quality to the physiological traits of organisms that generate population-level patterns (Sterner & Elser, 2002). Much evidence suggests that N content determines plant nu- tritional quality for a wide range of terrestrial insect herbivores (White, 1993). For example, N levels in foliage are usually more than an order of magnitude less than levels in insect tissue (Mattson, 1980) and higher N availability often increases devel- opment rate and survival for insect herbivores (Hunter & McNeil, 1997; Joern & Behmer, 1997). As a result, N availability is predicted generally to limit the spatial distributions and population growth rates of insect herbivores – the N limitation hypothesis (White, 1993). Although rarely considered, other nutrients such as phosphorus (P) may also affect the population Correspondence: Adam D. Kay, Department of Biology, University of St. Thomas, St. Paul, MN 55105, U.S.A. E-mail: adkay@stthomas.edu Fire effects on insect herbivores in an oak savanna: the role of light and nutrients ADAM D. KAY 1 , JOHN D. SCHADE 2 , MEGAN OGDAHL 3 , ELEONORE O. WESSERLE 3 and SARAH E. HOBBIE 3 1 Department of Biology, University of St. Thomas, St. Paul, Minnesota, U.S.A. 2 Department of Environmental Studies, St. Olaf College, Northfield, Minnesota, U.S.A. and 3 Department of Ecology, Evolution and Behavior, University of Minnesota, St. Paul, Minnesota, U.S.A. Abstract. 1. Environmental heterogeneity created by prescribed burning provided the context for testing whether the distribution of an oak specialist (the lace bug, Corythuca arcuata) could be explained by stoichiometric mismatches between herbivore and host plant composition. 2. Field observations showed that lace bug density was seven-fold higher in frequently burned than in unburned units. 3. Lace bug density did not increase with leaf nutrient concentrations, but was instead associated with higher light levels, higher concentrations of leaf carbon (C), lignin and total phenolics, and lower levels of cellulose. In addition, lace bugs reared on high-light leaves had higher levels of survivorship than those fed on low-light leaves. 4. Sampling restricted to full-sun leaves was used to test whether fire-related changes in leaf nitrogen (N) and phosphorus (P) concentrations have a secondary influence on lace bug success. This sampling provided only limited evidence for nutrient limitation, as decreases in leaf N and P were associated with an increase in lace bug mass but a decrease in density. 5. It is concluded that burning probably promotes lace bug population growth by increasing canopy openness, light penetration, and the availability of C-based metabolites, and thus simple stoichoimetric mismatches between herbivores and host plants are not of primary importance in this system. Key words. Body size, carbon quality , ecological stoichiometry , herbivory , leaf chemistry , nitrogen, phosphorus, plant–insect interactions, Quercus.