Aphids link different sensory modalities to accurately interpret ambiguous cues

When cues from the environment might be interpreted in several contrasting ways, animals need to precisely discern their exact source to avoid a wrong decision. We show that aphids are able to choose how to react to an unreliable cue through its association with a reliable cue from another sensory source (multimodal integration). For aphids, air movement or plant vibration may denote the danger of an approaching mammalian herbivore but may also represent adverse abiotic conditions. Aphids thus face a dilemma: Although the former interpretation requires aphids to evade the threat of being eaten by the mammal, the latter necessitates holding on to the host plant to avoid dislodgement. This ambiguity makes responding to the unreliable cues by themselves too risky. By noting the time lag between these unreliable cues and a reliable cue for mammalian presence, aphids finely modulate their response and accurately react to the perceived danger. When the reliable and unreliable cues were temporally close, aphids dropped more readily, probably because the unreliable cue was associated with mammalian presence. As the time lag between the 2 cues increased, the dropping response significantly decreased. This reduced dropping rate was not the result of a physiological constraint, but a behavioral mechanism most probably to reduce the chance of being dislodged by winds. Proper interpretation of unreliable multimodal cues can thus be improved through dynamically linking these cues and noting their temporal proximity.