BEHAVIOR Conspecifics Enhance Attraction of Vespula germanica (Hymenoptera: Vespidae) Foragers to Food Baits P. D’ADAMO, 1,2 M. LOZADA, 3 AND J. CORLEY 2 Ann. Entomol. Soc. Am. 96(5): 685Ð688 (2003) ABSTRACT Local enhancement has been shown to occur in the social wasp Vespula germanica (F.), a species that feeds on live insects as well as on dead animals. Some studies suggest local enhancement is based on sight, whereas others suggest that odors emanating from wasp bodies are more important in attracting conspecifc workers to a food source. We studied whether the attraction of V. germanica foragers to meat baits increases by the addition of live conspeciÞc foragers and analyzed which cues (olfactory and visual) elicit this attraction. Our results show that the combination of meat and wasps strongly enhances the attraction of conspeciÞc foragers. Presenting both visual and olfactory cues together leads to a wasp response that is much greater than if isolated visual or isolated olfactory cues were added, suggesting some synergistic action of both cues. KEY WORDS social insect communication, yellowjackets, German wasp, local enhancement, ol- factory cues THE CUES THAT foraging wasps use for prey location and choice appears to depend on both the spatial scale in which the hunting takes place and on the type of prey (Raveret-Richter and Jeanne 1985). The variability observed in foraging behavior suggests that the hunt- ing tactics of social wasps are likely to be facultative and situation dependent (Raveret-Richter 2000). Some social wasp species hover near stationary prey in response to visual cues and land in response to olfac- tory cues (Raveret-Richter and Jeanne 1985), whereas others land in response to visual cues alone (Duncan 1939, Jeanne 1972, Heinrich 1984). For instance, var- ious species of Vespula workers scavenging on protein orient in response to olfactory cues emanating from the resource (Rau 1944, Gaul 1952, Ross et al. 1984), while foraging on arthropod prey is largely mediated by visual cues (Brian and Brian 1952, Free 1970). Previous studies on mechanisms of meat discovery by V. germanica (Fabricius) and V. maculifrons (Buys- son) concluded that containers offering both visual and olfactory cues attracted more foragers than did containers offering either cue on its own (Reid et al. 1995). Controversy exists on the capacity of V. germanica to recruit conspeciÞcs to a food source (Overmyer and Jeanne 1998). However, it is a well-known fact that foraging workers tend to land and feed on resources being exploited by conspeciÞcs rather than on empty patches (Parrish and Fowler 1983, Reid et al. 1995, Raveret-Richter and Tisch 1999, DÕAdamo et al. 2000). For the same species, Reid et al. (1995) studied ag- gregation behavior of conspeciÞcs on a meat food source, and found that more wasps were at a bait, more conspeciÞcs were attracted to it. Recently, DÕAdamo et al. (2000) provided evidence that the attraction of V. germanica foragers can be elicited by wasp presence alone, and this might be mediated by odor cues pro- duced in glands located in the head (DÕAdamo et al. 2000). Vespula germanica is a member of the V. vulgaris group, which commonly supplement arthropod prey by scavenging on vertebrate carrion to feed larvae (Akre and MacDonald 1986). This scavenging behav- ior can become a nuisance to people involved in var- ious economic and recreational activities, such as bee- keeping, tourism, and horticulturism, particularly during late summer and early fall when yellowjackets are very abundant (Greene 1991). Vespula germanica, originally from Eurasia and Northern Africa, has in- vaded several regions of the world and has become a major pest (Edwards 1976, Akre and MacDonald 1986). In Argentina, it has rapidly spread throughout the country in the last 20 yr in one of the most out- standing insect invasions ever recorded for the region (Farji-Brener and Corley 1998). In this study we analyzed whether the addition of live conspeciÞcs to meat bait increases the attraction of V. germanica foragers. We also examined the rela- tive role that visual and olfactory cues have on landing behavior of foraging wasps. Materials and Methods The experimental design consisted of an array of six clean plastic containers (8 cm diameter, 10 cm high), 1 E-mail: pdadamo@bariloche.inta.gov.ar. 2 Laboratorio de Ecologõ ´a de Insectos Forestales, INTA EEA Bar- iloche, CC 277 - (8400) Bariloche, Argentina. 3 Laboratorio Ecotono, Universidad Nacional del Comahue, Pasaje Gutierrez 1125 - (8400) SC Bariloche, Rõ ´o Negro, Argentina. 0013-8746/03/0685Ð0688$04.00/0  2003 Entomological Society of America Downloaded from https://academic.oup.com/aesa/article/96/5/685/133773 by guest on 24 November 2022