The within-nest behaviour of honeybee pollen foragers in colonies with a high or low need for pollen

Numerous studies have documented that honeybee colonies can rapidly adjust the number of foragers collecting pollen in response to changes in quantities of brood, pollen and nectar in the nest. However, few studies have examined the behaviour of individual pollen foragers while in the nest between trips. Thus, little is known about how a pollen forager actually assesses its colony's needs. To understand this process better, we observed the behaviour of 319 pollen foragers while in their nests between foraging trips. We observed foragers in two types of nest environments: one with a relatively high need for pollen and one with a relatively low need for pollen. Foragers performed as many as 14 activities during two phases demarcated by the unloading of pollen loads. They inspected empty cells and cells with pollen, and performed the waggle dance at higher relative frequencies before unloading (P≤ 0.0004 each act). They antennated nestmates, autogroomed and received trophallaxis at higher relative frequencies after unloading (P≤ 0.0004 each act). All acts were performed both before and after unloading, but not always by each bee. Pollen foragers discriminated among cells based on cell contents in two contexts. First, they inspected cells already containing pollen more often than expected by chance. Second, their pattern of inspecting cells with different contents differed from their pattern of unloading pollen loads in those cells. Pollen foragers performed 42.3±4.6% (least square mean±SE) of preunloading inspection events on empty cells, but unloaded in them only 19.9±4.6% of the time. They performed 42.2±4.6% of preunloading inspection events on cells already containing pollen, but unloaded in them 79.4±4.6% of the time (P< 0.0001). Our data show that pollen foragers can determine the contents of cells in the nest and suggest that the regulation of pollen collection involves direct assessment of colony need by pollen foragers. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Cannibalism and early instar survival in a larval damselfly

Cannibalism by larval damselflies late in larval development on larvae a few instars smaller has been widely documented. I examine here the survival of eggs oviposited near the end of the flight season of adult Enallagma boreale in the presence and absence of potential cannibals, individuals that hatched from eggs earlier in the season, over an extended part of the life-cycle. The role of competition as a modifier of cannibalism was examined by manipulating egg density, environmental productivity, and habitat complexity. Survival in the absence of potential cannibals ranged from 5% to nearly 50% but was only 0–3% in the presence of cannibals. Survival of small larvae was related to manipulations of habitat complexity but not initial density or resources. There were no significant interactions of the presence of large larvae with other experimental treatments on the survival of small larvae. The mean size of small larvae was greater in the presence of cannibals. This may be because the cannibalism treatment reduced the density of small larvae and reduced competition for resources, or that the cannibals preferentially fed on small larvae and only relatively large individuals remained. Fertilization of the habitat or manipulating the initial density of small larvae did not affect mass of small larvae at the end of the experiment, which would be expected if small larvae were affected by competition for resources. Potential cannibals, however, emerged at higher mass when small larvae were present at low density and when productivity of the habitat was increased. This suggests that the negative effect of competition by small larvae outweighs the positive effect of being potential prey for large larvae.     

Biological effects of a 765-kV transmission line: Exposures and thresholds in honeybee colonies

Honeybee colonies exposed under a 765-kV, 60-Hz transmission line at 7 kV/m show the following sequence of effects: 1) increased motor activity with transient increase in hive temperature; 2) abnormal propolization; 3) impaired hive weight gain; 4) queen loss and abnormal production of queen cells; 5) decreased sealed brood; and 6) poor winter survival. When colonies were exposed at 5 different E fields (7, 5.5, 4.1, 1.8, and 0.65–0.85 kV/m) at incremental distances from the line, different thresholds for biologic effects were obtained. Hive net weights showed significant dose-related lags at the following exposures: 7 kV/m, one week; 5.5 kV/m, 2 weeks; and 4.1 kV/m, 11 weeks. The two lowest exposure groups had normal weight after 25 weeks. Abnormal propolization of hive entrances did not occur below 4.1 kV/m. Queen loss occurred in 6 of 7 colonies at 7 kV/m and 1 of 7 at 5.5 kV/m, but not below. Foraging rates were significantly lower only at 7 and 5.5 kV/m. Hive weight impairment and abnormal propolization occur at lower E-field intensity than other effects and limit the “biological effects corridor” of the transmission line to approximately 23 m beyond a ground line projection of each outer phase wire. Intrahive E fields of 15–100 kV/m were measured with a displacement current sensor. Step-potential-induced currents up to 0.5 μA were measured in an electrically equivalent bee model placed on the honeycomb in a hive exposed at 7 kV/m. At 1.8 kV/m body currents were a few nanoamperes, or two orders of magnitude lower, and these colonies showed no effects. E-field versus electric shock mechanisms are discussed.     

The influence of queen age and quality during queen replacement in honeybee colonies

Honeybee, Apis mellifera, colonies replace their queens by constructing many queen cells and then eliminating supernumerary queens until only one remains. The ages of the queens and the variation in their reproductive potential are important factors in the outcome of such events. Selection would favour colonies that requeen as quickly as possible to minimize the brood hiatus, therefore selecting for queens reared from older larvae. Conversely, reproductive potential (queen 'quality') is maximized by rearing queens from younger larvae. This potential trade-off was tested during two phases of queen replacement, namely queen rearing and polygyny reduction. Our results suggest that queen age is a significant element during both queen rearing and polygyny reduction, whereas queen quality, at least to the magnitude tested in this experiment, has little impact on the outcome of either process. The rate of queen replacement therefore appears to be an important factor in the honeybee life cycle, and further mechanisms of potential importance during this life history transition are discussed. Copyright 2000 The Association for the Study of Animal Behaviour.     

The hive bee to forager transition in honeybee colonies: the double repressor hypothesis

In summer, the honeybee (Apis mellifera) worker population consists of two temporal castes, a hive bee group performing a multitude of tasks including nursing inside the nest, and a forager group specialized on collecting nectar, pollen, water and propolis. Elucidation of the regulatory mechanisms responsible for the hive bee to forager transition holds a prominent position within present day sociobiology. Here we suggest a new explanation dubbed the "double repressor hypothesis" aimed to account for the substantial amount of empirical data in this field. This is the first time where both the regular transition and starvation-induced precocious transition are explained within the same regulatory framework. We suggest that the transition is under regulatory control by an internal and an external repressor of the allatoregulatory central nervous system, where these two repressors modulate a positive regulatory feedback loop involving juvenile hormone (JH) and the lipoprotein vitellogenin. The concepts of age-neutrality, fixed and variable response thresholds and reinforcement are integral parts of our explanation, and in addition they are given explicit physiological content. The hypothesis is represented by a differential equations model at the level of the individual bee, and by a discrete individual-based colony model. The two models generate predictions in accordance with empirical data concerning the cumulative probability of becoming a forager, mean age at onset of foraging, reversal of foragers, time window of reversal, relationship between JH titre and onset of foraging, relative representations of genotypic groups, and effects of forager depletion and confinement.     

Interadult feeding of jelly in honeybee (Apis mellifera L.) colonies

Summary Honeybee nurses (8 days old) were injected with ¹⁴C-phenylalanine. These bees then dispensed the ¹⁴C-labelled protein-rich products of their hypopharyngeal glands to the queen and the brood, and also to young drones and workers of all age classes. In small colonies containing 400–800 bees, nearly one-quarter of the radioactivity which could not be recovered in the nurses was fed by them in a protein-bound form to other members of the worker caste. During one night, one nurse fed an average of 4–5 foragers with proteinaceous food. The role of nurses in the work allotment system of honeybee colonies therefore needs a new, extended definition. Nurses are largely responsible for preparing nutrients from pollen, which is difficult to digest. They then distribute the nutritionally valuable protein produced by their hypopharyngeal glands to practically all hive mates.Dedicated to Professor Dr. O. Kepka on the occasion of his 65th birthday     

Stability of oxytetracycline in diets fed to honeybee colonies for disease control

Antibiotic extender patties, pollen patties, and sugar solutions containing oxytetracycline hydrochloride (OTC) were incubated at freezer (−9°C), refrigerator (4°C), room (25°C), and brood nest temperature (34°C) for 1, 2, 3, 7, and 11 weeks to determine the stability of the antibiotic. The OTC in antibiotic extender patties and pollen patties was stable at brood nest temperature for at least 11 weeks. The OTC in sugar solutions degraded within 1 week at brood nest temperature.     

Reproductive strategy and the life cycle in graptoloid colonies

Urbanek, A. 1990 10 15: Reproductive strategy and the life cycle in graptoloid colonies. Lethaia , Vol. 23, pp. 333–340. Oslo. ISSN 0024–1164.
Graptoloid colonies were clones composed in all probability of hermaphroditic zooids. Their breeding system approaching that of amphicarpic plants, namely distant out crossing combined with selfing, was exceptionally flexible. Moreover, the balanced coexistence of these extreme means of reproduction may be visualized as an evolutionarily stable strategy (ESS). The evolutionary consequences of such a breeding system might have accounted for the overall high rates of graptoloid evolution as well as for the rapid transformations in large populations. Sexual reproduction of graptoloid colonies was complemented by a multiplication through occasional fragmentation of colonies and subsequent regeneration from the fragments. Fragmentation of colonies played an important role in the survival of graptoloid colonies during catastrophic events such as hurricanes and later in recruitment. Fragmentation followed by regeneration, and only later by sexual reproduction of regenerated fragments, constituted the so-called great cycle (GC), whereas the regular course of events initiated by sexual reproduction in an undisturbed (complete) colony resulted in normal colony formation (astogeny) and is termed the small cycle (SC). Thus the adaptive significance of the sexual process in the life cycle is in the restoration of the perfect' pattern of the complete colony, which offered the best hydrodynamic properties and highest fitness. ▭ Graptolithina, Graptoloidea, breeding sysfem, reproductive strategy, fragmentation, life cycle .     

Waggle dances in absconding colonies of the red dwarf honeybee, Apis florea

The directional information encoded in the waggle dances of absconding colonies of Apis florea shows how different sites are advertised during decision-making. Colonies of A. florea were observed from the inception of absconding until the swarm settled at a new nest site. The number of waggle dancers at the beginning of the absconding sequence was low, gradually increased and then declined shortly before liftoff. During the last 2 to 0.5?h before liftoff, the dances still indicated different directions. This significantly decreased in the last 0.5?h until only one or two dance directions were being advertised. All colonies reached a near consensus in the last 20 dances before liftoff. The swarm flight path is meandering so the actual distance flown is about twice that indicated by the dances. During the last 3?min the waggle dance in most colonies showed nest target angles that were closely clustered indicating that the final directions advertised were close to the chosen target site. In all absconding/migratory species of honeybees thus far studied, there is a special dance associated with absconding that appears not to select specific destinations but rather a particular direction in search of a new nesting area.     

Relations between Funerary Cannibalism and Warfare Cannibalism: The Question of Predation

The Wari’, a southern Amazonian group of the Txapakura linguistic family, ate their dead and their enemies until at least the beginning of the 1960s. This article argues the continuity between these two forms of cannibalism by demonstrating that the Wari’ conceive the ingestion of the dead as a means of transforming them into prey. Predation – a defining characteristic of Amerindian warfare cannibalism – comprises a crucial means of differentiating two terms set in relationship, whether these terms be allies and enemies, the Wari’ and animals, or the living and the dead. In a world peopled by actual or potential human subjects, to transform the other into prey is to guarantee oneself the exclusive position of human, despite this being an essentially temporary position.     

Selectable components of sex allocation in colonies of the honeybee (Apis mellifera L.)

Colonies of social insects that undergo fission as a componentof reproduction produce large excesses of males. Hypothesesto explain this phenomenon have assumed that the workers thatconstitute the entourage for the new queen (or queens) representinvestment in female reproductives. Selection for optimal colonysex allocation then leads to an increase in production of malesthat balances the investment in females based on their relativereproductive values. We show that the construction of comb dedicatedto the production of males (drone comb) versus workers (workercomb) is a component of sex investment under the control ofcolony workers. Relative comb construction was highly correlatedwith the relative investment in male and worker brood. Coloniesthat invested relatively more in their total numbers of malesinvested less in the dry weight of individual workers. Coloniesthat had more adult workers produced a greater number of malesand workers, but colony size did not affect the proportionalinvestment in drone comb or brood. Genetic variability was foundfor the number of adult workers in colonies, the amount of dronecomb produced, the amount of worker comb produced, and the dryweight of adult workers, suggesting that sex allocation is aselectable trait in honeybees.     

Environmental impact of early palaeometallurgy: pollen and geochemical analysis

Interdisciplinary research was carried out in mid-level mountain areas in France with the aim of documenting historical mining and smelting activities by means of pollen and geochemical analyses. These investigations were made on cores collected in French peatlands in the Morvan (northern Massif Central), at Mont Lozère (southern Massif Central) and in the Basque Country (Pyrénées). Different periods of mining were recognised from Prehistory to modern times through the presence of anthropogenic lead in peat. Some of these were already known from archaeological dates or historical archives, especially for mediaeval and modern periods. However prehistoric ancient mining activities, as early as the Middle Bronze Age (ca. 1700 b.c.), were also discovered. They had all led to modifications in plant cover, probably related in part to forest clearance necessary to supply energy for mining and smelting.     

Differential proteomics in dequeened honeybee colonies reveals lower viral load in hemolymph of fertile worker bees

The eusocial societies of honeybees, where the queen is the only fertile female among tens of thousands sterile worker bees, have intrigued scientists for centuries. The proximate factors, which cause the inhibition of worker bee ovaries, remain largely unknown; as are the factors which cause the activation of worker ovaries upon the loss of queen and brood in the colony. In an attempt to reveal key players in the regulatory network, we made a proteomic comparison of hemolymph profiles of workers with completely activated ovaries vs. rudimentary ovaries. An unexpected finding of this study is the correlation between age matched worker sterility and the enrichment of Picorna-like virus proteins. Fertile workers, on the other hand, show the upregulation of potential components of the immune system. It remains to be investigated whether viral infections contribute to worker sterility directly or are the result of a weaker immune system of sterile workers.     

Influence of pollen diet in spring on development of honey bee (Hymenoptera: Apidae) colonies

The effects of changes in spring pollen diet on the development of honey bee, Apis mellifera L. (Hymenoptera: Apidae), colonies were examined in a 3-yr study (2002-2004). Pollen-supplemented and pollen-limited conditions were created in colonies every spring, and brood rearing and honey yields were subsequently monitored throughout the summer. In all 3 yr, colonies that were supplemented with pollen or a pollen substitute in the spring started rearing brood earlier than colonies in other treatment groups and produced the most workers by late April or early May. In 2002, these initial differences were reflected by a two-fold increase in annual honey yields by September for colonies that were pollen-supplemented during the spring compared with pollen-limited colonies. In 2003 and 2004, differences between treatment groups in the cumulative number of workers produced by colonies disappeared by midsummer, and all colonies had similar annual honey yields (exception: in one year, productivity was low for colonies supplemented with pollen before wintering). Discrepancies between years coincided with differences in spring weather conditions. Colonies supplemented with pollen or a substitute during the spring performed similarly in all respects. These results indicate that an investment in supplementing the pollen diet of colonies would be returned for situations in which large spring populations are important, but long-term improvement in honey yields may only result when spring foraging is severely reduced by inclement weather. Beekeepers should weigh this information against the nutritional deficiencies that are frequently generated in colonies by the stresses of commercial management.     

Olfactory information transfer in the honeybee: compared efficiency of classical conditioning and early exposure

We investigated the ability of honeybees, Apis mellifera, to use olfactory information gained in a given experimental context, in other contexts. First, restrained bees were subjected to a Pavlovian associative learning procedure, based on the conditioning of the proboscis extension response (PER), where a floral odour was paired with a sugar reward. We observed the orientation behaviour of conditioned and na?ve bees in a four-armed olfactometer with four contiguous fields either scented with the conditioning odour or unscented. Information transfer was clearly shown, conditioned bees orienting towards the conditioning odour, whilst na?ve bees shunned it. Second, the effect of passive olfactory exposures during the bees' development was assessed in two behavioural contexts: either orientation in the olfactometer or a PER conditioning procedure. Two exposure periods were applied: (1) the pupal stage (9 days before emergence); (2) the early adult stage (8 days after emergence). No effect of preimaginal exposure was recorded, but exposure during the early adult stage induced a higher choice frequency of the odour field in the olfactometer, and lower learning performance in the PER conditioning assay. These observations show that olfactory information gained during development can modify bees' later behaviour in different contexts: this is another instance of olfactory information transfer in bees. These results also suggest that nonassociative learning phenomena, taking place at a critical period during development, might be involved in the maturation of the bees' olfactory system, and in the organization of odour-mediated behaviours. Copyright 2000 The Association for the Study of Animal Behaviour.