Three-dimensional flight analysis shows associative learning enhances foraging behavior of the specialist parasitoid, Microplitis croceipes

The reproductive fitness of parasitoids is dependent on their ability to find optimal hosts for oviposition and nectar/honeydew as a sugar source for survival and reproduction. Learning of ecologically relevant odors helps parasitoids refine their foraging behavior to enhance their reproductive success. However, little is known about how associative learning may help parasitoids optimize their flight behavior while foraging for food and/or hosts. This study compared the inflight behavioral responses of naïve and experienced Microplitis croceipes (Cresson) (Hymenoptera: Braconidae) toward two ecologically relevant, host-related volatile compounds, α-pinene and α-farnesene. Using wind tunnel bioassays, we tested the hypothesis that associative learning of ecologically relevant odors would improve the flight responses of M. croceipes females, resulting in oriented and motivated flight toward the odor sources. A behavioral tracking software, which records the flight behavior of insects in three dimensions, was used to track the inflight behaviors of naïve and experienced parasitoids to ecologically relevant odors (α-pinene and α-farnesene) and compare relevant flight-related parameters (response time, time in upwind flight, speed, angular velocity, and tortuosity). The results showed that associative learning significantly improved the foraging behavior of M. croceipes females. Odor learning resulted in more directly oriented upwind flight toward odor sources compared to naïve females. In addition, comparisons of individual flight parameters revealed that learning enables parasitoids to adapt to specific cues, thereby increasing responsiveness and attractiveness to the learned odor. These findings highlight the adaptive significance of associative learning during foraging and host location strategies in parasitoids.