Allocation of Colony‐Level Foraging Effort in Vespula germanica in Response to Food Resource Quantity, Quality, and Associated Olfactory Cues

Abstract

In social insects, selection takes place primarily at the level of the colony. Therefore, unlike solitary insects, social species are expected to forage at rates that maximize colony fitness rather than individual fitness. Workers can increase the net benefit of foraging by responding to increased resource availability, by responding more strongly to higher‐quality resources, and by decreasing the uncertainty with which nestmates find resources. Unlike many ants and social bees, no social wasp is known to utilize a nest‐based recruitment signal to inform nestmates of food location. On the other hand, wasps do learn the odor of food brought to the nest and use this cue to locate the food source outside the nest. Here, we quantify the effects of three food‐associated variables on the allocation of foraging effort in the yellowjacket Vespula germanica. We used an experimental approach to assess whether resource quantity, quality, or associated olfactory information affect the probability that a forager will leave the nest on a foraging trip. We addressed these questions by inserting a known amount of sucrose solution directly into nests and recording foraging effort (departure rate) over the subsequent hour‐long observation period. No differences were found in foraging effort because of the presence/absence of olfactory cues, but there was strong evidence that foraging effort increased in response to resource influx and resource quality. Thus, while olfactory cues are learned in the nest, only resource quality and the cue of increased amount of food in the nest factor into a forager's decision of whether or not to depart on a foraging trip. However, as prior work has shown, once a wasp forager leaves the nest, it uses the learned olfactory cues to aid in finding resources.

Nest-based information transfer and foraging activation in the common wasp (Vespula vulgaris)

“…Our results on the food choice of naïve V. vulgaris foragers parallel similar results on V. germanica (Overmyer and Jeanne 1998). Trophallaxis represents one possible mechanism for achieving this transfer of information, as discussed for other wasp species such as V. germanica (Overmyer and Jeanne 1998;Taylor et al 2010Taylor et al , 2011Taylor et al , 2012a and P. occidentalis (Schueller et al 2010). The role of trophallactic exchanges in foraging information transfer and associative learning was demonstrated in bees and ants (Farina et al 2005;Farina 1996;Provecho and Josens 2009).…”

“…We therefore interpret our results as evidence for a conditional, plastic response at the colony level to the availability of resources in the field. The rapid increase in foraging traffic rate of the trained colony, corresponding to an increase in the food brought back to the nest, is similar to that recorded by Taylor et al (2012a) when inserting food in V. germanica nests. To our knowledge, we have demonstrated for the first time that a measurable colony response can be triggered by the activity of free-flying, trained wasps, without the insertion of the resource inside the nest.…”

“…Despite some reports (Naumann 1970;Taylor 2012), there is no clear evidence that social wasps (Hymenoptera: Vespidae) use signals to recruit nestmates to food sources (Raveret-Richter 2000;Jeanne and Taylor 2009;Nieh 2009). The giant hornet, Vespa mandarinia, is the only wasp known to utilize a field-based recruitment signal.…”

“…Although the traditional view is that foraging in social wasps is an individual activity (Raveret-Richter 2000), several studies have highlighted that cue-mediated forms of information transfer and co-ordination appear to occur amongst foragers (e.g., Overmyer and Jeanne 1998;Schueller et al 2010;Taylor 2012). In the German wasp, Vespula germanica, and in Polybia occidentalis, scent extracts diluted in sucrose presented in training feeders, or directly inserted in the nest, were associated with food by naïve wasps and used as cues to detect resources outside the nest (Overmyer and Jeanne 1998;Taylor et al 2010;Schueller et al 2010;Taylor et al 2011Taylor et al , 2012a.…”

“…In the German wasp, Vespula germanica, and in Polybia occidentalis, scent extracts diluted in sucrose presented in training feeders, or directly inserted in the nest, were associated with food by naïve wasps and used as cues to detect resources outside the nest (Overmyer and Jeanne 1998;Taylor et al 2010;Schueller et al 2010;Taylor et al 2011Taylor et al , 2012a. This food-related transfer of information may take place in the field (e.g., local enhancement) and at the nest (e.g., foraging activation) (Nieh 2009).…”