Pattern recognition in honeybees: chromatic properties of orientation analysis

The spectral properties of the discrimination of pattern orientation in freely flying honeybees (Apis mellifera) were examined. Bees were trained to discriminate between two random black/white gratings oriented perpendicularly to each other, one of which was associated with a reward. Subsequently the bees were tested on two-colour gratings or gratings consisting of grey and coloured stripes, providing a range of different chromatic contrasts, luminance contrasts and specific channel contrasts. The results of these experiments indicate that orientation analysis in the honeybee is mediated almost exclusively by the green receptor channel, although the bee's visual system as a whole is endowed with excellent trichromatic colour vision.     

Number of adult female mites Varroa jacobsoni Oud. on hive debris from honey bee colonies artificially infested to monitor mite population increase (Mesostigmata: Varroidae)

Six honey bee colonies hived in Langstroth nuclei were each artificially infested with 100 phoretic Varroa mites. Hive debris on bottom inserts was inspected every 3–4 days. The adult Varroa mites were compared with mounted specimens and catalogued into lightly pigmented and darkly pigmented females. After 4 months, an acaricide treatment was used to estimate the final mite population. Based on light and dark adult counts, we propose a balancing equation that follows the Varroa population increase at 7 day intervals and allows the calculation of experimental population growth rates. The calculated Varroa finite rate of increase is =1.021. Exponential and logistic growth models fitted to the balancing equation data gave R ²=0.986 and R ²=0.991, respectively. To develop a more precise model it would be necessary to follow the population growth beyond our experimental data.     

Host-seeking behaviour of tracheal mites (Acari: Tarsonemidae) on honey bees (Hymenoptera: Apidae)

The behaviour of the endoparasitic tracheal mite, Acarapis woodi (Rennie) on honey bees (Apis mellifera L.) is a challenge to observe because of its small size. Through a microscope, we videotaped this mite's movement on young bees, dead bees and bees exposed to vegetable oil. Previous studies have shown that solid vegetable oil decreases mite infestations in a bee colony. We hypothesized that the oil alters mite behaviour to the detriment of the parasite, thus helping to safeguard the host. Habitat-seeking behaviour, identified as necessary for mites to locate a new host environment, was disrupted on both dead and oil-treated bees. Questing behaviour, which is associated with transfer between hosts, increased significantly on the dead and oily bees. The behaviours of mites were significantly different between all three treatments (x ²=494.96, p<0.001 on dead bees and x ²=851.11, p<0.001 on oily bees). Both questing and seeking behaviours were significantly different on each of the thoracic treatments (F _2,66=7.88, p<0.001 and F _2,66=21.28, p<0.001) and mite questing behaviour was not altered between males and females on live or oily bees (F _1,22=0.25, p<0.62), but habitat seeking was (F _1,22=7.42, p<0.012). The male questing and habitat-seeking behaviours were observed. We conclude that oil-treated bees gained protection from habitat-seeking mites because the normal behaviour of the mites seeking an oviposition site is interrupted.     

Comparative study of the antennal lobes and their afferent pathway in the worker bee and the drone (Apis mellifera)

Summary The topography of the antennal afferent path-ways was studied comparatively in the worker bee and the drone of Apis mellifera L. by cellular marking, following localized application of cobalt chloride to the cut end of one antenna. This study dealt principally with the first relay of the afferent pathway in the glomeruli of the antennal lobe. The counting and measurement of all the glomeruli were performed on 5 worker bees and 5 drones. An important sexual dimorphism, represented by 4 large and easily identifiable glomerular complexes, was demonstrated in the drone. In both worker bee and drone, four main regions of the glomerular neuropil were distinguished according to corresponding afferent bundles. The worker possessed 166 glomeruli and the drone 103. The number, position and dimensions of the glomeruli indicated that the glomerular organization was unvarying in worker bees and in drones. Concerning the internal structure of the glomeruli, two types were distinguished: the great majority (95%) exhibited a cortical layer, whereas in the 7 posterior glomeruli the synaptic fields of association seemed to be scattered throughout the whole volume. The main results of this work (glomerular invariance, sexual dimorphism) support the hypothesis of the functional unit of the glomeruli.Unité de Recherche Associée au CNRS, UA 483     

“Spraying” Behavior During Queen Competition in Honey Bees

In honey bees (Apis mellifera), virgin queens may eject a liquid substance from their abdomens while they are engaged in fatal combat. We investigated the functional significance of spraying behavior by staging queen duels within colonies housed in observation hives. Spraying occurred in 39.7% of all interactions between rival queens and was recorded in 12 of 15 duels. Workers were highly attracted to the surfaces and individuals contaminated by spraying, forming tight clusters with hundreds of bees in which movement was severely restricted. One or both queens in a pair became immobilized by the workers in 37.5 and 29.2% of all spraying events, respectively, but the queens were never killed by the workers. Conversely, a mobile queen penetrated the worker aggregation and stung an immobilized queen in one-third of the observed bouts. Thus spraying may serve as a fighting tactic by virgin queens to increase their chances of winning by temporarily immobilizing their rivals.     

The time course of dark adaptation in the bee: a phototactic and electrophysiological investigation

ABSTRACT. The time course of dark adaptation in Apis melifera L. was investigated by analyses of phototactic behaviour and electroretinogram (ERG). The behavioural results give a function for dark adaptation showing that in the dark after strong light adaptation the sensitivity increases exponentially with a time constant of 3 min. The sensitivity changes c. 2.4 log units during the time span of 5–720 s. The electrophysiological results indicate a smaller change in sensitivity at the level of the photoreceptors. Within a time span between 20 and 720 s the sensitivity increases during dark adaptation by a factor of 4.3 on a linear scale.