A. P. Martin

An interspecific comparison of foraging range and nest density of four bumblebee (Bombus) species

Bumblebees are major pollinators of crops and wildflowers in northern temperate regions. Knowledge of their ecology is vital for the design of effective management and conservation strategies but key aspects remain poorly understood. Here we employed microsatellite markers to estimate and compare foraging range and nest density among four UK species: Bombus terrestris, Bombus pascuorum, Bombus lapidarius, and Bombus pratorum. Workers were sampled along a 1.5‐km linear transect across arable farmland. Eight or nine polymorphic microsatellite markers were then used to identify putative sisters. In accordance with previous studies, minimum estimated maximum foraging range was greatest for B. terrestris (758 m) and least for B. pascuorum (449 m). The estimate for B. lapidarius was similar to B. pascuorum (450 m), while that of B. pratorum was intermediate (674 m). Since the area of forage available to bees increases as the square of foraging range, these differences correspond to a threefold variation in the area used by bumblebee nests of different species. Possible explanations for these differences are discussed. Estimates for nest density at the times of sampling were 29, 68, 117, and 26/km2 for B. terrestris, B. pascuorum, B. lapidarius and B. pratorum, respectively. These data suggest that even among the most common British bumblebee species, significant differences in fundamental aspects of their ecology exist, a finding that should be reflected in management and conservation strategies.

Flight metabolic rate and Pgi genotype influence butterfly dispersal rate in the field.

Dispersal is a key life-history trait, especially in species inhabiting fragmented landscapes. The process of dispersal is affected by a suite of morphological, physiological, and behavioral traits, all of which have a more or less complex genetic basis and are affected by the prevailing environmental conditions. To be able to identify genetic and phenotypic effects on dispersal, movements have to be recorded over relevant spatial and temporal scales. We used harmonic radar to track free-flying Glanville fritillary butterflies (Melitaea cinxia) released in the field and reconstructed their flight tracks for several hours. Flight track lengths for individual butterflies ranged from tens of meters to several kilometers. Butterflies were most mobile at midday and in intermediate temperatures. Flight metabolic rate (MR), measured prior to the tracking, explained variation in mobility at all scales studied. One-third of the variation in the distance moved in one hour could be attributed to variation in flight MR. Heterozygous individuals at a single nucleotide polymorphism in the phosphoglucose isomerase (Pgi) gene moved longer distances in the morning and at lower ambient temperatures than homozygous individuals. A similar genotype x temperature interaction was found to affect the metabolic rate. Our results establish connections from molecular variation in a single gene to flight physiology and movement behavior at the landscape level. These results indicate a fitness advantage to the heterozygous genotype in low temperatures and suggest a mechanism by which varying environmental conditions maintain genetic polymorphism in populations.

Tracking butterfly movements with harmonic radar reveals an effect of population age on movement distance

We used harmonic radar to track freely flying Glanville fritillary butterfly (Melitaea cinxia) females within an area of 30 ha. Butterflies originated from large and continuous populations in China and Estonia, and from newly established or old (> 5 years) small local populations in a highly fragmented landscape in Finland. Caterpillars were raised under common garden conditions and unmated females were tested soon after eclosion. The reconstructed flight paths for 66 individuals comprised a total distance of 51 km with high spatial resolution. Butterflies originating from large continuous populations and from old local populations in Finland exhibited similar movement behaviors, whereas butterflies originating from newly established local populations in the fragmented landscape in Finland moved significantly more than the others. There was no difference in the lengths of individual flight bouts, but the new-population females flew more frequently, resulting in longer daily movement tracks. The flight activity of all individuals was affected by environmental conditions, peaking at 19–23°C (depending on population type), in the early afternoon, and during calm weather. Butterflies from all population types showed a strong tendency to follow habitat edges between the open study area and the neighboring woodlands.

Bumblebee nest density and the scale of available forage in arable landscapes

Abstract. 1 Combining the needs of agricultural production with enhancing biodiversity requires a landscape‐scale approach since the geographic scale at which most non‐farmed species operate is unconstrained by farm boundaries. Bumblebees are a key component of farmland biodiversity as pollinators of both crops and wild flora. However, the factors determining their densities in such landscapes remain poorly understood. 2 Using a combination of remote‐sensed landscape data and molecular markers, we quantify the effects of land use (oilseed rape, field beans and non‐cropped areas, all of which provide suitable bumblebee forage), at various spatial scales to find the best predictor of colony density for the bumblebee Bombus pascuorum Scopoli in an arable landscape. 3 Estimated colony density was positively correlated with the area of all habitat categories within 1000 m of the sample site. No significant relationships were found for greater or lesser distances. This concurs with earlier estimates of the foraging range of this species. We found no evidence that nest sizes increased with forage availability, although our data do not allow us to categorically exclude this possibility. 4 It has long been suspected that forage availability limits bee abundance in agricultural landscapes but there is little direct evidence for this. Here we report a direct relationship between floral abundance and bumblebee nest density within a notionally fixed area. Importantly, we suggest that the forage availability within the previously published estimated foraging distance for this species at this location is a good predictor of the scale of impact of forage provision on nesting density.

(Z)-11-eicosen-1-ol, an important new pheromonal component from the sting of the honey bee,Apis mellifera L. (Hymenoptera, Apidae.)

Abstract(Z)-11-Eicosen-1-ol was identified by GC-MS and microchemical methods as a major volatile component, ca. 5 μg per insect, secreted by the sting apparatus of the worker honey bee. When presented on moving lures at the hive entrance, (Z)-11-eicosen-1-ol, like isopentyl acetate already known as an alarm pheromone, elicited stinging, and together these two compounds were as active as the natural pheromone from the sting. On stationary lures, (Z)-11-eicosen-1-ol prolonged the effectiveness of isopentyl acetate.

Nasonov pheromone of the honey bee, Apis mellifera L. (Hymenoptera, Apidae) Part I. Chemical characterization.

Composition of the Nasonov pheromone of the honey bee has been reexamined using new procedures, including analysis of pheromone from single live insects by capillary column GC-MS. Two new components have been identified, nerol and (E,E)-farnesol, and the presence of components proposed previously has been confirmed. Absolute amounts or relative proportions of components in the pheromonal secretion have been determined.

The effects of non‐host plant essential oil volatiles on the behaviour of the pollen beetle Meligethes aeneus

The use of semiochemicals for manipulation of the pollen beetle Meligethes aeneus (Fabricius) (Coleoptera: Nitidulidae) is being investigated for potential incorporation into a push‐pull control strategy for this pest, which damages oilseed rape, Brassica napus L. (Brassicaceae), throughout Europe. The response of M. aeneus to non‐host plant volatiles was investigated in laboratory assays to establish whether they have any effect on host plant location behaviour. Two approaches were used. First a novel, moving‐air bioassay using air funnels was developed to compare the response of M. aeneus to several non‐host plant essential oils. The beetles avoided the host plant flowers in the presence of non‐host volatiles, suggesting that M. aeneus uses olfactory cues in host location and/or acceptance. The results were expressed as ‘repellency values’ in order to compare the effects of the different oils tested. Lavender (Lavendula angustifolia Miller) (Lamiaceae) essential oil gave the highest repellency value. In addition, a four‐arm olfactometer was used to investigate olfactory responses, as this technique eliminated the influence of host plant visual and contact cues. The attraction to host plant volatiles was reduced by the addition of non‐host plant volatiles, but in addition to masking the host plant volatiles, the non‐host volatiles were avoided when these were presented alone. This is encouraging for the potential use of non‐host plants within a push‐pull strategy to reduce the pest colonisation of crops. Further testing in more realistic semi‐field and field trials is underway.

Honeybees use a Lévy flight search strategy and odour-mediated anemotaxis to relocate food sources

The availability of food resources changes over time and space, and foraging animals are constantly faced with choices about how to respond when a resource becomes depleted. We hypothesise that flying insects like bees discover new food sources using an optimal Lévy flight searching strategy and odour-mediated anemotaxis, as well as visual cues. To study these searching patterns, foraging honeybees were trained to a scented feeder which was then removed. Two new unrewarding feeders, or ‘targets’, were then positioned up- and downwind of the original location of the training feeder. The subsequent flight patterns of the bees were recorded over several hundred metres using harmonic radar. We show that the flight patterns constitute an optimal Lévy flight searching strategy for the location of the training feeder, a strategy that is also optimal for the location of alternative food sources when patchily distributed. Scented targets that were positioned upwind of the original training feeder were investigated most with the numbers of investigations declining with increasing distance from the original feeder. Scented targets in downwind locations were rarely investigated and unscented targets were largely ignored, despite having the same visual appearance as the rewarding training feeder.

Could learning of pollen odours by honey bees (Apis mellifera) play a role in their foraging behaviour

Abstract.  The role of pollen odour cues in the foraging behaviour of honey bees (Apis mellifera L.) is poorly understood. Using classical conditioning of the proboscis extension response, in which bees learn to associate an odour with a sucrose reward, the present study tests whether odours of bee‐collected pollen from the hive environment or odours of fresh pollen on the anthers of flowers could be used in pollen foraging. Honey bees efficiently learn odours from field‐bean (Vicia faba) bee‐collected pollen and oilseed‐rape (Brassica napus) bee‐collected pollen, hand‐collected pollen, anthers and whole flowers, demonstrating that honey bees can learn pollen odours associatively in biologically realistic concentrations. Honey bees learn pollen odours of oilseed rape better than field bean and, although they generalize these two odours, they easily distinguish between them in discrimination tests, suggesting that pollen odours may be used in species recognition/discrimination. There is little evidence that honey bees can recognize whole flowers based on previous experience of bee‐collected pollen odour. However, they generalize the odours of oilseed‐rape anthers and whole flowers, suggesting that anther pollen in situ may play a more prominent role than bee‐collected pollen in foraging behaviour.

Nasonov pheromone of the honey bee,Apis mellifera L. (Hymenoptera, Apidae). part III. : Regulation of pheromone composition and production.

GC and GC-MS analyses of the multicomponent Nasonov pheromone of the honey bee, and of the air above insects releasing the pheromone, show that constant composition is maintained during release, despite differing volatilities of the components. The regulating mechanism may involve a specific enzyme process, detected in excised Nasonov glands, which converts the major component geraniol into the more volatile (E)-citral. Analysis of honey bees of known ages and at different times of year shows that maximum secretion occurs when foraging is most likely.