Jean-Claude Verhaeghe

Probabilistic behaviour in ants: A strategy of errors?

Animal behaviour is probabilistic. This is exemplified by the communication behaviour of ants during food-searching. Experimental evidence demonstrates that species differ in the accuracy of their recruitment. We show here, with the help of a very simple mathematical model, that the randomness of behaviour can have an adaptative advantage for ants. The model demonstrates that the degree of randomness could be optimally “tuned” to particular ecological conditions, such as food quantity and distribution.

ABSOLUTE CONFIGURATION OF (3R,4S)-4-METHYL-3- HEXANOL--A PHEROMONE FROM THE HEAD OF THE ANT TETRAMORIUM IMPURUM FOERSTER

Abstract The isolation of 4-methyl-3-hexanol and 4-methyl-3-hexanone from the heads of all adult castes of T. impurum (previously wrongly reported as T. caespitum is described. The important quantitative differences between the secretions of both sexes is confirmed, males producing much higher quantities of both compounds. The absolute configuration of the alcohol from the heads of males was found to be 3R,4S. In view of the sexual differences observed in T. impurum , the qualitative divergence in the secretions of T. impurum and T. caespitum is tentatively interpreted as a biochemical isolation mechanism between two sibling species.

Is the caste-ratio of the oligolectic bumblebee Bombus gerstaeckeri Morawitz (Hymenoptera: Apidae) biased to queens?

Abstract Three bumblebee species, foraging on Aconitum spp. have been commonly observed in Eyne (France, East Pyrénées): Bombus gerstaeckeri, B. hortorum and B. wurflenii. We estimated the population of these three species. For B. hortorum and B. wurflenii, the total workers populations foraging on Aconitum spp. ranged from 101 to 523 and 156 to 270, respectively. These two species also forage on other plants while B. gerstaeckeri visits only Aconitum spp. The population of B. gerstaeckeri observed was extremely small, founded by 33 queens only in 2001. With a total number of workers estimated from 40 to 102, the observed workers/queens ratio, 1 to 3 workers for each queen, is very unusual for a eusocial species. Also we observed queens foraging during the whole life of the colony. This kind of social organisation is similar to that of some high arctic species. It could be interpreted as the result of an insularity syndrome.

Caste-dependent pheromones in the head of the antTetramorium caespitum

The heads of maleT. caespitum contain 4-methyl-3-hexanol (1.7 μg, only the erythro isomer(s) detected) and 4-methyl-3-hexanone (0.8 μg). The heads of alate females contain 0.1 μg of each compound, whereas only the alcohol (0.1 ⧎g) was found in the heads of workers. Both compounds act as attractants for the workers and their possible functions are discussed.