The role of lateral optic flow cues in hawkmoth flight control

ABSTRACT Flying animals require sensory feedback on changes of their body position, as well as on their distance from nearby objects. The apparent image motion, or optic flow, which is generated as animals move through the air, can provide this information. Flight tunnel experiments have been crucial for our understanding of how insects use optic flow for flight control in confined spaces. However, previous work mainly focused on species from two insect orders: Hymenoptera and Diptera. We therefore set out to investigate whether the previously described control strategies to navigate enclosed environments are also used by insects with a different optical system, flight kinematics and phylogenetic background. We tested the role of lateral visual cues for forward flight control in the hummingbird hawkmoth Macroglossum stellatarum (Sphingidae, Lepidoptera), which possesses superposition compound eyes, and has the ability to hover in addition to its capacity for fast forward flight. Our results show that hawkmoths use a similar strategy for lateral position control to bees and flies in balancing the magnitude of translational optic flow perceived in both eyes. However, the influence of lateral optic flow on flight speed in hawkmoths differed from that in bees and flies. Moreover, hawkmoths showed individually attributable differences in position and speed control when the presented optic flow was unbalanced. Summary: Hummingbird hawkmoths use optic flow similarly to flies and bees to control their position, but not their speed, in flight tunnel experiments.