SUMMARY The production of multimodal signals during animal displays is extremely common, and the function of such complex signaling has received much attention. Currently, the most frequently explored hypotheses regarding the evolution and function of complex signaling focus on the signal and/or signaler, or the signaling environment, while much less attention has been placed on the receivers. However, recent studies using vertebrates suggest that receiver psychology (e.g. learning and memory) may play a large role in the evolution of complex signaling. To date, the influence of multimodal cues on receiver learning and/or memory has not been studied in invertebrates. Here, we test the hypothesis that the presence of a seismic (vibratory)stimulus improves color discrimination learning in the jumping spider Habronattus dossenus. Using a heat-aversion learning experiment, we found evidence for a cross-modal effect on color learning. Over a series of training trials, individuals exposed to a seismic stimulus jumped onto the heated color less frequently and remained there for less time than did individuals not exposed to a seismic stimulus. In addition, in a final no-heat test trial, individuals from the seismic-present treatment were more likely to avoid the previously heated color than were individuals from the seismic-absent treatment. This is the first study to demonstrate a cross-modal influence on learning in an invertebrate.

Spatial learning has been examined in a variety of animals to determine what cues are used to navigate through a complex environment. A common feature of previously studied vertebrates and invertebrates is their need to return to a previously visited site for mating, nesting, foraging or predator avoidance. Velvet ants (Hymenoptera: Mutillidae) are cursorial parasitoids with flightless females that must walk through complex terrain to find ground dwelling host larvae burrows. Velvet ants are not central-place foragers (they do not return to an established nest site) so much of the previous work on spatial learning does not directly apply in this context. It was assumed that females primarily use chemosensory cues for navigation and burrow location instead of visual learning. This study, however, demonstrates that velvet ant females are able to use visual landmarks to find an inconspicuous exit in an aversion-motivation spatial learning task. A significant number of velvet ants learned to locate the exit after seven training trials and went to the previous location of the exit even after the maze had been rotated, showing that landmarks external to the maze were used to learn the escape location.