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In an important digression, John Philopon delivers a theory of his own on light as incorporeal energeia. Several difficulties arise from this. How can we explain that something incorporeal can produce heat in the air? For heat comes from the friction of two bodies. How can we explain that something incorporeal can be reflected in a mirror and produce an angle? For an angle is a matter of size, and size is related to corporeality. The author immerses us fully in a seminar of Ammonius of Hermias, whose reportator he is., Jean Philopon livre ici, à l’occasion d’une importante digression, une théorie qui lui est propre sur la lumière comme energeia incorporelle. Plusieurs difficultés en découlent. Comment expliquer qu’un incorporel puisse produire de la chaleur dans l’air ? Car la chaleur provient de la friction de deux corps. Comment expliquer qu’un incorporel puisse se réfléchir dans un miroir et produire un angle ? Car l’angle relève de la grandeur et la grandeur ressortit à la corporéité. L’auteur nous immerge en plein séminaire d’Ammonius d’Hermias dont il est le reportator.

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La présente contribution se propose de signaler un certain nombre de matériaux faisant difficulté dans les études platoniciennes, à savoir, le statut de la subjectivité humaine d’une part, et la question du divin d’autre part, ainsi que la difficulté de leur rapport respectif. De tels domaines, on le sait, sont particulièrement délicats à manipuler tant il est vrai qu’il est facile d’opérer toutes sortes de croisements entre la façon somme toute assez sobre dont Platon considérait le divin et...

Idipsum est une locution qu’Augustin utilise pour désigner Dieu. Elle signifie littéralement « cela même ». Ce minimalisme sémantique ne laisse pas de la rendre mystérieuse. Faut-il y voir un emprunt à certains textes bibliques qui déjà en font usage ? Dans ce cas, idipsum, tel un nom propre vide de toute signification, se bornerait à indiquer Dieu en tant qu’il échappe à toute définition rationnelle. Ou bien faut-il rattacher idipsum à la tradition platonicienne qui recourt à des locutions grecques similaires pour désigner la réalité intelligible qui est « elle-même en elle-même » ? Idipsum serait alors la trace d’un héritage philosophique conduisant Augustin à une définition métaphysique de Dieu comme Être absolu. Cependant, cette alternative entre origine biblique et tradition platonicienne néglige la diversité des usages philosophiques des locutions formées sur auto puis ipsum : elles expriment d’abord l’identité et le fait d’être soi, puis la réflexivité, au croisement des champs dialectique, pratique et ontologique. Cet ouvrage explore la façon dont ces aspects de l’identité se sont construits, du autos grec à l’idipsum latin, à travers des études portant sur Homère, Platon, Aristote, le stoïcisme, le néoplatonisme grec puis latin, Augustin.

International audience

National audience; Varroa resistance can be defined as the ability of honey bee colonies to survive the parasite for several years in the absence of any treatment against the mite. Long-term survival of untreated Apis mellifera populations has been reported in the US and Europe. The ability of honey bee colonies to survive varroa mite infestations has been associated with the development of Varroa Sensitive Hygiene behavior (VSH). Resistant colonies are able to detect the presence of varroa through the cap of developing brood cells and to remove parasitized brood and the mites. To improve breeding programs for varroa resistance, detailed knowledge of the mechanisms that enable bees to survive mite infestation and environmental conditions that can influence the expression and evaluation of VSH behavior are needed. This study aims at evaluating the influence of the coloniy population dynamics, the varroa density in colonies, he task allocation strategy and the food supply on the ability of colonies to expres the VSH trait. Such efforts are particularly important to standardize testing in different locations, a feature that is essential to ensure the success of breeding efforts.

International audience; Honeybee colonies are increasingly exposed to environmental stress factors, which can lead to their decline or failure. However, there are major gaps in stressor risk assessment due to the difficulty of assessing the honeybee colony state and detecting abnormal events. Since stress factors usually induce a demographic disturbance in the colony (e.g. loss of foragers, early transition from nurse to forager state), we suggest that disturbances could be revealed indirectly by measuring the age- and task-related physiological state of bees, which can be referred to as biological age (an indicator of the changes in physiological state that occur throughout an individual lifespan). We therefore estimated the biological age of bees from the relationship between age and biomarkers of task specialization (vitellogenin and the adipokinetic hormone receptor). This relationship was determined from a calibrated sample set of known-age bees and mathematically modelled for biological age prediction. Then, we determined throughout the foraging season the evolution of the biological age of bees from colonies with low (conventional apiary) or high Varroa destructor infestation rates (organic apiary). We found that the biological age of bees from the conventional apiary progressively decreased from the spring (17 days) to the fall (6 days). However, in colonies from the organic apiary, the population aged from spring (13 days) to summer (18.5 days) and then rejuvenated in the fall (13 days) after Varroa treatment. Biological age was positively correlated with the amount of brood (open and closed cells) in the apiary with low Varroa pressure, and negatively correlated with Varroa infestation level in the apiary with high Varroa pressure. Altogether, these results show that the estimation of biological age is a useful and effective method for assessing colony demographic state and likely detrimental effects of stress factors.

From the SETAC Pellston Workshop on Pesticide Risk Assessment for Pollinators 15-21 January 2011 Pensacola, Florida, USA; International audience

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