Sensitivity and feeding efficiency of the black garden ant Lasius niger to sugar resources

International audienceCarbohydrate sources such as plant exudates, nectar and honeydew represent the main source of energy for many ant species and contribute towards maintaining their mutualistic relationships with plants or aphid colonies. Here we characterise the sensitivity, feeding response curve and food intake efficiency of the aphid tending ant, Lasius niger for major sugars found in nectar, honeydew and insect haemolymph (i.e. fructose, glucose, sucrose, melezitose and trehalose). We found that sucrose concentrations - ranging from 0.1 to 2.5 M - triggered food acceptance by L. niger workers with their food intake efficiency being enhanced by sugar concentrations of 1 M or higher at which points energy intake was maximised. The range of sucrose concentrations that elicit a feeding response by L. niger scouts thus overlaps with that of natural sugar resources. The response curves of feeding acceptance by scouts consistently increased with sugar concentration, except for trehalose which was disregarded by the ants. Ants are highly sensitive to sucrose and melezitose exhibiting low response thresholds. Sucrose, fructose and glucose share a same potential to act as phagostimulants as they had similar half feeding efficiency concentration values when expressed as the energetic content of sugar solution. Aphid-biosynthezised melezitose generated the highest sensitivity and phagostimulant potential. The feeding behavior of ants appears to be primarily regulated by the energy content of the food solution for the main sugars present in nectar and honeydew. However, feeding by scouts is also influenced by the informative value of individual sugars when it serves as a cue for the presence of aphid partners such as the aphid-biosynthesised melezitose

Extinction of ants' feeding and social foraging on myrmecochorous seeds

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The effect of nest topology on spatial organization and recruitment in the red ant Myrmica rubra

Nests of social insects are an important area for the exchange of food and information among workers. We investigated how the topology of nest chambers (as opposed to nest size or environmental factors) affects the spatial distribution of nestmates and the foraging behavior of Myrmica rubra ant colonies. Colonies were housed in artificial nests, each with same-sized chambers differing in the spatial arrangement of galleries. A highly connected central chamber favored higher occupancy rates and a more homogeneous distribution of ants across chambers. In contrast, a chain of successive chambers led to a more heterogeneous distribution of ants, with the occupancy of a chamber chiefly mediated by its distance to the entrance. Irrespective of nest topology, the entrance chamber housed the largest proportion of ants, often including the queen, which exhibited a preference for staying in densely populated chambers. Finally, we investigated how nest topology influenced nestmate recruitment. Surprisingly, a highly connected chamber in the center of the nest did not promote greater recruitment nor activation of ants. At the onset of foraging, the largest number of moving ants was reached in the topology where the most connected chamber was the nest entrance. Later in the process, we found that a chain of successive chambers was the best topology for promoting ant’s mobilization. Our work demonstrates that nest topology can shape the spatial organization and the collective response of ant colonies, thereby taking part in their adaptative strategies to exploit environmental resources.info:eu-repo/semantics/publishe

Aphid Alarm Pheromone as a Cue for Ants to Locate Aphid Partners

The mutualistic relationships that occur between myrmecophilous aphids and ants are based on the rich food supply that honeydew represents for ants and on the protection they provide against aphid natural enemies. While aphid predators and parasitoids actively forage for oviposition sites by using aphid semiochemicals, scouts of aphid-tending ant species would also benefit from locating honeydew resources by orienting toward aphid pheromone sources. The present study aims to provide additional information on the use of Aphis fabae alarm pheromone, i.e. (E)-β-farnesene (EβF), by ant scouts. The perception and behavioral impact of EβF on Lasius niger were investigated using electroantennography and two bio-assays measuring their attraction and orientation towards aphid semiochemicals. Pronounced electrical depolarizations were observed from L. niger scout antennae to stimulations of A. fabae alarm pheromone, while other sesquiterpenes elicited weak or no responses. L. niger scouts were significantly attracted toward EβF in a four-arm olfactometer, as well as in an two-choice bioassay. These laboratory results suggest for the first time that low amounts of aphid alarm pheromone can be used by L. niger scouts as a cue indicating the presence of aphid colonies and could therefore mediate the aphid-ant partnership in the field.Peer reviewe

The Formation of Collective Silk Balls in the Spider Mite Tetranychus urticae Koch

Tetranychus urticae is a phytophagous mite that forms colonies of several thousand individuals. These mites construct a common web to protect the colony. When plants become overcrowded and food resources become scarce, individuals gather at the plant apex to form a ball composed of mites and their silk threads. This ball is a structure facilitating group dispersal by wind or animal transport. Until now, no quantitative study had been done on this collective form of migration. This is the first attempt to understand the mechanisms that underlie the emergence and growth of the ball. We studied this collective behaviour under laboratory conditions on standardized infested plants. Our results show that the collective displacement and the formation of balls result from a recruitment process: by depositing silk threads on their way up to the plant apex, mites favour and amplify the recruitment toward the balls. A critical threshold (quorum response) in the cumulative flow of mites must be reached to observe the emergence of a ball. At the beginning of the balls formation, mites form an aggregate. After 24 hours, the aggregated mites are trapped inside the silk balls by the complex network of silk threads and finally die, except for recently arrived individuals. The balls are mainly composed of immature stages. Our study reconstructs the key events that lead to the formation of silk balls. They suggest that the interplay between mites' density, plant morphology and plant density lead to different modes of dispersions (individual or collective) and under what conditions populations might adopt a collective strategy rather than one that is individually oriented. Moreover, our results lead to discuss two aspects of the cooperation and altruism: the importance of Allee effects during colonization of new plants and the importance of the size of a founding group

Field study on foraging by the polymorphic ant Pheidole pallidula

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Rôle des glandes de l'appareil à venin dans la communication chez Messor Barbarus (Hymenoptera, Formicidae)

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Dealing with complexity: Intelligent decision criteria in ant societies

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Noodopgravingen aan de Burchtgracht (1988) :het secreet van Sint-Ontcommer (3de deel)

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