Marie-Claire Cammaerts Tricot

Phéromones stimulant et inhibant l'agressivité chez Myrmica rubra

Abstract The aggressiveness of Myrmica rubra workers is stimulated by their poison gland secretion. On the other hand, the major compound of the mandibular gland, 3-octanone, markedly suppresses their aggressiveness. The inhibitory activity of 3-octanone is still effective when dissolved in liquid paraffin at a concentration of 10 −9 vol./vol. At a concentration 100 times greater in liquid paraffin, 3-nonanone may also suppress the aggressiveness of the ants. This substance however represents only a trace of the mandibular secretion. Neither 6-methyl-3-octanone, nor 3-octanol, possesses an inhibitory effect on the aggressiveness of the ants even when present in liquid paraffin at a concentration 10 4 times greater than the lowest effective dilution of 3-octanone. The relative proportions of 3-octanol and 3-octanone vary greatly in the mandibular gland secretion of the workers from the same nest or from different nests of the same species. The proportions of 3-octanol in the mixture of octanol+octanone present in the vapour released by one crushed worker head range from 4·6 to 38·0 per cent. The histogram of these proportions is unimodal, with the mode situated near 15 per cent of 3-octanol. A mixture of 3-octanol and 3-octanone in liquid paraffin, releasing a vapour containing 15 per cent of 3-octanol, has no more activity than a solution containing only 3-octanone. There is no reason to believe so far that a mixture of 3-octanol and 3-octanone of precise composition has any particular meaning for the ants. We suggest that the ants when attacked emit the inhibitory and stimulative pheromones in such a way that the aggressiveness of the alarmed workers is directed toward the enemy without their being themselves the victims of this aggressiveness.

Piste et phéromone attractive chez la fourmi Myrmica rubra

SummaryAMyrmica rubra worker deposits the attractant secretion of its Dufours gland when walking around an ant of another species (e.g.Lasius flavus).If theLasius is not killed, the worker walks to the nest, laying a trail of the secretion of its poison glands secretion (Fig. 2).The worker reaches the nest, meets members of the society and walks back to theLasius, depositing a trail of the attractive secretion of its Dufours gland (Fig. 3).The trail attracts many ants to the place where help is needed.A Myrmica rubra worker deposits the attractant secretion of its Dufours gland when walking around an ant of another species (e.g. Lasius flavus). If the Lasius is not killed, the worker walks to the nest, laying a trail of the secretion of its poison glands secretion (Fig. 2). The worker reaches the nest, meets members of the society and walks back to the Lasius, depositing a trail of the attractive secretion of its Dufours gland (Fig. 3). The trail attracts many ants to the place where help is needed.

A 0.123% Stevia/Aspartame 91/9 Aqueous Solution Balances the Effects of the Two Substances, and may thus be a Safer and Tastier Sweetener to be Used

Sweeteners are presently largely consumed all over the world, essentially aspartame (North America, Europe) and stevia (South America, Asia). Aspartame has a pleasant taste but present some adverse effects; stevia has very few adverse effects but has not the sweetest taste. Using ants as biological models, we here examined if a 0.123% solution of stevia/aspartame 91/9 might have both a pleasant taste and nearly no adverse effects. We found that it did not change the ants’ food consumption while aspartame increased it and stevia slightly decreased it. It did not affect their locomotion, precision of reaction and response to pheromones as aspartame did. It did not increase their audacity as aspartame largely and stevia somewhat did. It did not affect the ants’ brood caring behavior and cognition as aspartame did, and it did not impact the conditioning ability and memory as aspartame drastically and stevia slightly did. Confronted to sugar water and a stevia/aspartame 91/9 solution, the ants equally drunk the two solutions, while having the choice between aspartame and sugar, they soon nearly exclusively chose the sugar, and while in presence of stevia and sugar, the ants progressively chose the sugar. Very probably aspartame enhanced the taste of stevia, and as the latter contains a true glycoside, a stevia/aspartame 91/9 solution did not affect the ants’ physiology and ethology as pure aspartame did. In front of sugar and a stevia/aspartame ca 96/4 solution, the ants chose the sugar. Thus, a 0.123% solution in which 9% aspartame (and no less) is mixed to 91% stevia (and no more) appears to constitute a safe and tasty sweetener which could be used instead of solutions containing only aspartame or stevia.