IntroductionIn ectotherms, most physiological processes are strongly influenced by body temperature (Huey 1982;Heinrich 1993). Sensitivity to temperature has the potential to influence the behaviour, ecology and, ultimately, fitness of an individual. The extent to which ectotherms can tolerate changes in their ambient thermal environment is thus critical in determining their distribution and abundance.There are two broad strategies by which an ectotherm can adapt to its thermal environment:1. Be a thermal generalist (eurythermal) and evolve a physiology that is relatively insensitive to temperature change and which confers a broad range of temperature tolerance. 2. Be a temperature specialist (stenothermal), with a physiology adapted to a relatively narrow range of temperatures. There are then two alternative strategies possible, either (a) a low body temperature optimum close to ambient temperatures, or Ectotherms may be thermal generalists, or high-or low-temperature thermal specialists. The thermal strategy of four species of grasshoppers occurring in Britain is determined, where unpredictable variation in the generally cool climate should preclude the low-temperature thermal specialist strategy. It is predicted that temperature sensitivity will determine geographical distribution, with generalist species widespread, and thermally specialized species restricted to warmer habitats. 2.The developmental and reproductive responses to different rearing temperatures of the grasshoppers are examined in a laboratory experiment. Life-history traits are integrated into a fitness model to determine the sensitivity of each species to temperature change.3. Growth and development rates increased with temperature for each species. The frequency with which an additional instar was inserted during nymphal development increased with temperature in Chorthippus brunneus. Adult mass and size increased with temperature. 4. Egg pod production rate increased with temperature. In Omocestus viridulus, Myrmeleotettix maculatus and Stenobothrus lineatus, temperature had no effect on egg mass, eggs per pod or number of pods per female. Number of pods per female increased with temperature in C. brunneus. 5. Fitness of S. lineatus decreased by 88% for a 5°C fall in temperature compared with 58% and 56% for C. brunneus and M. maculatus, respectively. Omocestus viridulus is least sensitive to temperature change with only a 27% reduction in fitness at the lower rearing temperature. 6. It is concluded that all the species are high-temperature thermal specialists, and variation in their sensitivity to temperature is a good predictor of their distribution. The most generalist species, O. viridulus, is the most widespread, while the more specialist species S. lineatus and M. maculatus are restricted to warmer habitats. Chorthippus brunneus is also a high-temperature specialist, but is more widespread as a consequence of developmental and reproductive plasticity and efficient behavioural thermoregulation.

Selective logging has been the main cause of disturbance to tropical forests in Southeast Asia, so the extent to which biodiversity is maintained in selectively logged forest is of prime conservation importance. We compared the butterfly assemblages of Bornean primary rainforest to those of rainforest selectively logged 6 years previously. We sampled by means of replicated transects stratified into riverine and ridge forests and we included roads in the logged forest. There was a three‐fold variation in species richness and abundance over the 8‐month sampling period. More species and individuals were observed in the logged forest, although between‐replicate variability was high. Rarefied species richness was positively correlated with canopy openness within the range of disturbance levels encountered at our forest sites. Within families, there was no significant difference in the number of species between primary and logged forest. There was a significant difference in the relative abundance of species, but this was due largely to the abundance of one or two species. Community ordination separated the sites along a gradient of disturbance and revealed strong differences between riverine and ridge‐forest butterfly assemblages in primary forest that were obscured in logged forest. There was no evidence that logging has resulted in a change in the composition of the butterfly assemblages from species with a local distribution to more widespread species. We conclude that at a logged forest site in close proximity to primary forest, low intensities of logging do not necessarily reduce the species richness or abundance of butterflies, although assemblage composition is changed.

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Summary1. This study examines the extent to which thermal balance and thermoregulatory ability may contribute to habitat partitioning in insect herbivores. 2. The distribution of four species of grasshopper on a Breckland grass heath is described. Myrmeleotettix maculatus is restricted to short swards, Omocestus viridulus is restricted to long swards, and Chorthippus brunneus and Stenobothrus lineatus are found on swards of intermediate length.3. Short swards are warmer on average than long swards, but lack cooler refuges on hot days. 4. Chorthippus brunneus and O. viridulus are better able to raise their body temperatures at low ambient temperatures than M. maculatus and S. lineatus. Omocestus viridulus is less able to reduce body temperature at high ambient temperature. 5. Myrmeleotettix maculatus may be precluded from inhabiting cooler long swards because of its inability to raise body temperatures at low ambient temperatures. Omocestus viridulus may avoid short swards because of the danger of overheating. 6. Thermoregulatory ability is a good predictor of the distribution of the grasshoppers in swards of differing length and microclimate.

Summary1. Moreno & Halffter (2000) described the problems associated with comparing species richness among communities that have inventories compiled using different methods or with different sampling effort. They used species accumulation curves to standardize samples among sites, to predict the species richness of sites and to estimate the minimum effort required for adequate completeness of inventories. 2. I argue that their measure of sampling effort, number of nights, is inappropriate because it does not distinguish between genuine differences in species richness among sites and differences in trap efficiency. The number of individuals is the best measure of sampling effort to avoid this problem, as illustrated by data on moths collected from a Bornean rainforest. Furthermore, the approach of Moreno & Halffter requires the species accumulation curves to be approaching an asymptote for accurate estimation, and so for practical reasons is probably limited to less diverse taxa.