Visual Learning in a Generalist Tachinid Parasitoid

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Tachinid flies are a diverse and ecologically important family of insect parasitoids. However, the means by which tachinid species locate and select hosts are poorly known. Many tachinids exhibit wide host ranges and possess well-developed visual systems. A series of behavioral assays using the generalist tachinid Exorista mella (Walker) (Diptera: Tachinidae) were conducted to assess the importance of visual cues in the process of host location and acceptance in this parasitoid. The capacity of E. mella to learn to associate visual cues with hosts was examined with additional experiments using colored disks. Female E. mella responded strongly to host motion in assays using both live hosts and host models and this cue is shown to be an important elicitor of attack behavior. Flies positively associated colored paper disks with the presence of hosts, indicating that they may employ visual learning of microhabitats associated with hosts, or of hosts themselves. Learning of visual cues associated with hosts by E. mella may allow this generalist parasitoid to take advantage of locally abundant host populations and maintain host-searching efficiency in an unpredictable environment.

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