Summary 1.Waggle dances of honey-bees ( Apis mellifera L . ) were decoded to determine where and how far the bees foraged during the blooming of heather ( Calluna vulgaris L.) in August 1996 using a hive located in Sheffield, UK, east of the heather moors. The median distance foraged was 6·1 km, and the mean 5·5 km. Only 10% of the bees foraged within 0·5 km of the hive whereas 50% went more than 6 km, 25% more than 7·5 km and 10% more than 9·5 km from the hive. 2. These results are in sharp contrast with previous studies in which foraging distances were much closer to the hive. In May 1997 the mean foraging distance was 1 km, showing that long-range dancing is not the rule in Sheffield. 3. The observed foraging distances described in this study may not be exceptional in a patchy environment where differences in patch size and patch quality are large. When travel distances to patches are large, distant patches can probably be utilized only by individuals that live in groups and recruit foragers to the patches found. Only then are the benefits of scouting for distant patches high enough to enable the exploitation of these patches.

Task partitioning is the name given to the phenomenon in which a piece of work is divided among two or more workers, such as the partitioning of the collection of a load of forage between a forager and a storer or transporter. This study 1) reviews empirical data concerning the occurrence of task partitioning in insect societies with the general aim of drawing broad conclusions about its prevalence and diversity, and 2) considers the potential costs and benefits of task partitioning. The data show that task partitioning occurs in many species, with examples in ants, bees, wasps, and termites. The general impression is that it is an important and widespread feature of work organisation in insect societies.Nearly all examples concern foraging. There is much variation on the main theme. For example, in the number of intersecting cycles (2, 3 linear, 3 all interlocking), where transfer occurs (at the nest, at the forage site, on the trail back to the nest), whether transfer is direct or indirect (liquids such as nectar, water, and honeydew are always transferred directly whereas solids are transferred both directly and indirectly). Task partitioning is always subject to time costs. Benefits occur either through enhancement of individual performance (e.g., where task partitioning permits greater division of labour thereby utilising consistent differences in worker abilities caused by morphology or experience) or through enhancement of the overall system (e.g., where partitioning itself eliminates a constraint affecting task performance, such as when a forager can collect sufficient material for several builders). By causing a series organisation of work, task partitioning reduces system reliability but this effect may be minimal in all but very small colonies.

In human society selfish use of common resources can lead to disaster, a situation known as the 'tragedy of the commons' (TOC). Although a TOC is usually prevented by coercion, theory predicts that close kinship ties can also favour reduced exploitation. We test this prediction using data on a TOC occurring in Melipona bee societies.

Understanding the evolution of multiple mating by females (polyandry) is an important question in behavioural ecology. Most leading explanations for polyandry by social insect queens are based upon a postulated fitness benefit from increased intracolonial genetic diversity, which also arises when colonies are headed by multiple queens (polygyny). An indirect test of the genetic diversity hypotheses is therefore provided by the relationship between polyandry and polygyny across species, which should be negative if the genetic diversity hypotheses are correct. Here, we conduct a powerful comparative investigation of the relationship between polyandry and polygyny for 241 species of eusocial Hymenoptera (ants, bees and wasps). We find a clear and significant negative relationship between polyandry and polygyny after controlling for phylogeny. These results strongly suggest that fitness benefits resulting from increased intracolonial genetic diversity have played an important role in the evolution of polyandry, and possibly polygyny, in social insects.

Worker bees eventually begin laying eggs in honey bee colonies that have lost their queen and have failed to rear a replacement. In contrast, workers tend to lack developed ovaries and tend to suppress drone production by worker nestmates in colonies with queens. We measured changes in worker egg-removal behaviour, ovary development, and egg-laying rate in hives following the removal of their queens. We carried out weekly assays of worker removal of experimentally transferred eggs, dissection and inspection of worker bee ovaries, and daily checks of worker oviposition. Following queen removal, the egg-removal rate by workers generally first increased, then decreased or levelled off over the four-week time course of the experiment; this behaviour was closely synchronized with the increase in worker ovary development and egg-laying. We discuss our results in the context of theoretically predicted worker-worker conflict over the onset of reproduction in queenless honey bee societies.

Summary 1.We compared the foraging behaviour of two small (approximately 6000 bees) and two large (approximately 20 000 bees) honey-bee colonies over 6 days. We determined where the bees of each colony foraged, whether they collected nectar or pollen, the number of patches foraged at, the number of bees engaged in foraging, and the concentration of the nectar collected. 2. Even though the colonies were located in the same environment and had the same genetic background, foragers from different colonies used different forage patches. 3. Small and large colonies foraged at a similar distance in July when forage was abundant (mean foraging distance for small and large colonies was 0·67 and 0·62 km, respectively) whereas the large colonies foraged significantly further in August when forage was scarce (mean foraging distance for small and large colonies was 1·43 and 2·85 km, respectively). 4. Small colonies foraged at approximately the same number of patches as large colonies. The total number of foragers returning to the small colonies per minute was significantly lower than the number of foragers returning to the large colonies. This means that, relative to their size, small colonies foraged at more patches than large colonies. 5. The quality of the nectar collected by foragers of the small and large colonies did not differ. However, small colonies did collect more pollen than large colonies.

Many ants use pheromone trails to organize collective foraging. This study investigated the rate at which a well-established Pharaoh's ant, Monomorium pharaonis (L.), trail breaks down on two substrates (polycarbonate plastic, newspaper). Workers were allowed to feed on sucrose solution from a feeder 30 cm from the nest. Between the nest and the feeder, the trail had a Y-shaped bifurcation. Initially, while recruiting to and exploiting the feeder, workers could only deposit pheromone on the branch leading to the feeder. Once the trail was established (by approximately 60 ants per min for 20 min), the ants were not allowed to reinforce the trail and were given a choice between the marked and unmarked branches. The numbers of ants choosing each branch were counted for 30 min. Initially, most went to the side on which pheromone had been deposited (80% and 70% on the plastic and paper substrates, respectively). However, this decayed to 50% within 25 min for plastic and 8 min for paper. From these data, the half-life times of the pheromone are estimated as approximately 9 min and 3 min on plastic and paper, respectively. The results show that, for M. pharaonis, trail decay is rapid and is affected strongly by trail substrate.

The struggle among social classes or castes is well known in humans. Here, we show that caste inequality similarly affects societies of ants, bees and wasps, where castes are morphologically distinct and workers have greatly reduced reproductive potential compared with queens. In social insects, an individual normally has no control over its own fate, whether queen or worker, as this is socially determined during rearing. Here, for the first time, we quantify a strategy for overcoming social control. In the stingless bee Schwarziana quadripunctata, some individuals reared in worker cells avoid a worker fate by developing into fully functional dwarf queens.