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Due to its multifunctional and complex role in the honey bee colony functioning and health (construction material allowing food storage, brood rearing, thermoregulation, mediation in chemical and m...

SummaryAs a possible way to help control varroa mites, some beekeepers advocate the use of cells smaller than the regular size commonly used by beekeepers. This paper addresses two of their principal arguments, namely that honey bees built smaller cells under natural conditions in the past, and that a “fatal” error occurred at the turn of the 20th century when a new and allegedly misleading method of estimating cell density was introduced. Historical data show not only that cell sizes were not smaller in the past, but also that estimating cell densities was not an issue before the introduction of wax foundation. Moreover, not realizing that the two methods of estimating cell densities are equivalent, the proponents of small cells have erroneously corrected the data reported by the authors of the 17th, 18th and 19th centuries. In conclusion, the claim that cells were smaller in the past is not only not supported by the historical records, but rests on a distortion of the historical records resulting from a...

Two series of cafeteria tests involving six varieties of Trifolium repens were conducted to confirm the preference of fossorial Arvicola terrestris for acyanogenic white clover (T. repens) and to investigate their responses to repeated exposures to toxic plants. The animals were offered the choice between two bunches of freshly harvested white clover. In 261 simple choice tests, 160 individuals were tested for various combinations of three acyanogenic and three cyanogenic varieties. They showed a clear preference for the acyanogenic morphs, both in comparisons between opposite cyanotypes and in two control situations involving either self-comparisons or comparisons between similar cyanotypes. In 320 repeated choice tests, 40 voles assigned to three groups (comparisons between opposite cyanotypes and control comparisons between similar cyanotypes) were tested eight times for the same alternative. They showed a persistent preference for the acyanogenic morph and significantly reduced their total food consumption when they had a strictly cyanogenic diet. In the latter case, they stored or wasted more plant material than in the other treatments. These voles also ingested high amounts of cyanide which suggests good detoxification abilities and a possible habituation to cyanide.

We report experimental results showing that, under both laboratory conditions as well as in outdoor enclosures, the fossorial vole Arvicola terrestris preferentially feeds on acyanogenic white clover (Trifolium repens) when offered the choice between two varieties (Ladino and Aran) differing highly in their content in cyanogenic glycosides. We also observed that the voles adapted their diet and reduced their relative consumption of the cyanogenic variety during experiments conducted for two to three weeks in outdoor enclosures as compared to shorter tests conducted for 48 hr in laboratory cages. In addition, we report a similar preference for the acyanogenic Ladino variety for the slugs Arion ater and A. subfuscus.

Levins and Ginzburg raised two paradoxes concerning the logistic equation of population growth. None of them received a satisfactory answer within the frame of the original equation. Here, we propose solutions to both paradoxes.

regulatory effects was obscured by linear and nonlinear trends in one and two cases, respectively. The data support the hypothesis that time-delayed and nonlinear mechanisms of population regulation oper- ate in fossorial populations of A. terrestris. Furthermore, the data are consistent with regulatory mechanisms involving predator-prey interactions, while the causation of the unusually long cycle is still an open question. Finally, the presence of trends in these time series suggests that water vole populations track some long-term climatic changes in the environment.

The golden hamster carries food back to its nest along a direct path. In a situation combining a passive outward journey with the elimination of visual and various other exteroceptive cues, the subjects continued to return to their nest site and were not influenced by alterations of the earth's magnetic field. Experiments in which the animals started their hoarding trips from a changing point of departure, or were transferred to an unfamiliar experimental space, suggest that they orientate by path integration and that they assess the angular, but not the linear component of a passive outward journey.

When hoarding food in an experimental arena (o = 2.20 m), golden hamsters tend to return along a direct path from the food source at the centre of the arena to their peripherally located nest. Under infra-red light the animals' homing behaviour is exclusively controlled by 'internal' cues which have been generated during the outward journey to the feeding place. The paper examines the limitations on the registration and computation of directional cues which originate from an active or a passive outgoing trip. The compensation of the angular component of the outward journey was examined by inducing the subjects to walk (actively) around the centre of the arena, or by rotating the animals (passively) on a platform which contained the food source. The greater the number of rotations, the less precise the homing performance. After three to five active rotations, and after two to three passive rotations of 360°, the animals ceased to yield significant homing vectors. Unidirectional rotations induced a systematic ipsidirectional bias, an indication of undercornpensation; no bias was observed after rotations which occurred in equal extents in both directions. Special importance was given to the compensation for passive translations. The experiments involved either the shift of the subjects from their nest exit to an unfamiliar, adjacent arena, or the combination of an active and a passive outward leg during the outward journey to the centre of the animals' own arena. During their return to the nest, either the hamsters did not take into account at all the direction of the passive translation, or if they did, the compensation was only limited. These results are discussed in relation to the animals' capacity to assess 1) an active outward journey through the availability of different categories of self generated cues, and 2) a passive outward journey predominantly on the basis of vestibular signals. A final series of experiments showed that under certain conditions, the hamsters commit systematic homing errors which can be attributed to their failure to initiate the registration and computation of path dependent cues at the right instant in time and space.

When hoarding food under IR light, the golden hamster returns to its nest by path integration after an active outward journey, and it is capable of compensating the angular component of a passive outward journey independently of auditory, olfactory, tactile and geomagnetic cues. If, however, peripheral visual cues are available, they predominate over information which is gained during the active or passive outward journey. Further experiments show the limitations of homing by path integration, which is open to cumulative errors and therefore needs to be complemented by other categories of information.