Foragers of Vespula germanica (Fab.) return to a food source that has not been depleted. In this work we investigate the utilisation of olfactory and visual cues by these foragers for relocating a specific source location. We trained wasp foragers to feed on a dish with either honey or meat. At the testing phase, we analysed searching and landing behaviour over three cues: the original feeding site, an unscented model of the food, and a container from which food odours emanated. We compared the responses of the foragers to the three cues and evaluated the effect of bait type with which wasps were trained. We found that landing responses are elicited mainly by odour cues in both protein- and carbohydrate-trained wasps. However, the type of food that wasps are exploiting influences their searching behaviour, as the number of hovers over the visual cue was higher when wasps were trained with carbohydrates whereas the number of hovers over the original feeding site was higher when wasps were trained with proteins.

The German yellowjacket Vespula germanica (F.) (Hymenoptera: Vespidae), an invasive wasp, is a highly efficient forager. We studied wasp cognitive ability while varying landmark disposition and cue conspicuity. Learning flights were used as an indicator of forager cognition while relocating a food source. We recorded the number of learning flights (circling above the food location) performed after each visit by each wasp. We studied the effect of modifying a learned location and analyzed how the addition of conspicuous cues affected wasp learning. Cognitive ability also was studied in relation to food manipulation efficiency, i.e., the time taken to extract a piece of meat and fly away. We found that one feeding visit was sufficient for wasps to learn relevant cues associated with a rewarded location, as shown by the reduction of learning flights after just one experience. Moreover, wasps reached asymptotic levels in food manipulation after only one feeding visit. The introduction of a contextual change, such as moving the food location a few centimeters from the original feeding site, affected returning foragers, who increased the number of learning flights when leaving the array. Interestingly, enriched contexts with conspicuous cues seemed to facilitate wasp cognition as they performed fewer learning flights than in nonenriched ones. Learning flights seem to be a good cognitive indicator, reflecting wasp experience with a certain context, thus revealing their sensitivity to landmark cue conspicuity. This study highlights the cognitive capacities of V. germanica foragers.

Social insects are known for their behavioural plasticity and learning abilities. In the present work, we evaluated whether a single past experience could influence Vespula germanica (F.) foraging behaviour by analysing wasp response in two changing situations: when food was displaced at different distances from a previously learned location and when the amount of resource was significantly decreased. In the former case, wasps were allowed to collect meat once from a dish which was later displaced 300, 600 or 900 mm from the previous location. Thus, on the second visit, wasps encountered an empty dish in place of the previously baited one. We recorded the time taken to find the displaced food, the number of hovers over the previously learned location and the direction of first approach of returning foragers. Wasps spent less time searching at the previously learnt site when the dish with food was displaced 300 mm rather than 600 or 900 mm from the learned location. In the second experiment, when two dishes with food were simultaneously offered, one containing 20 g and another 80 g, wasps preferred the 80 g dish. On their second visit, we switched the position of the dishes and recorded which dish wasps collected food from. We found that most wasps collected food from the previously learned location and not from the dish with the more abundant resource. This study illustrates the remarkable influence of a single collecting experience on V. germanica subsequent foraging behaviour.

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