The role of learning in adult food location by the larval parasitoid,Microplitis croceipes (Hymenoptera: Braconidae)

Wind tunnel experiments were conducted to determine roles of odor learning in food foraging of the larval parasitoid,Microplitis croceipes (Hymenoptera: Braconidae). Females that had neither fed on sucrose water nor experienced any odor and females that had experienced an odor without feeding failed to respond to any odors in a wind tunnel. Most of the females that had fed without an odor also did not respond to odors. However, most of the females that had experienced an odor during feeding on sucrose water flew to the odor. These results indicate that when females experience an odor during feeding, they learn to associate the odor with food and subsequently respond to the odor. As age of females increased, their response to an experienced odor increased, peaked 2 to 5 days after emergence, and then decreased. With an increasing number of odor experiences while feeding, accuracy of females choosing the experienced odor increased. Females that experienced an odor while feeding three to five times chose the experienced odor 90% of the time. When females experienced an odor while feeding five times, the memory of food associated odor lasted at least 2 days. When they experienced food with two odors successively, they could memorize both odors, and multiple experiences did not cause memory interference. Even when females had learned a food-associated odor, their response to the learned odor ceased after several visits on patches containing the odor but no food. Such negative experience may cause switching of food searching to new odors by females.