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Title: Antennal Regulation of Migratory Flight in the Neotropical Moth, Urania fulgens

item Srygley, Robert

Submitted to: Biology Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2010
Publication Date: 2/24/2010
Citation: Sane, S., Srygley, R.B., Dudley, R. 2010. Antennal Regulation of Migratory Flight in the Neotropical Moth, Urania fulgens. Biology Letters. 6:406-409.

Interpretive Summary: Conventionally it is thought that insects maintain a constant airspeed by visually referencing the ground and sensing the passing airstream with hairs on their head and the antennae. Due to difficulties inherent in tracking single individuals, the role of antennal input remained untested in freely migrating insects. We tracked individual moths as they migrated over Lake Gatun, Panama during the day and measured their airspeed. We captured the moths, experimentally amputated the flagellum of each antenna or only cut the very tip to serve as a control, and released them back over the lake. For those that could still fly, we measured their airspeed and orientation post-release. Most moths were unable to control flight and crashed into the lake after losing their antennae, but a reasonable fraction (41%) could fly. In addition, those capable of flying maintained the same airspeed but not the same migratory orientation as they had prior to antennal loss. Thus, regulation of airspeed may not require antennal input, whereas spatial orientation may depend on antennal integrity. This knowledge improves our understanding of how insects move between suitable habitats such as agricultural fields.

Technical Abstract: Migrating insects use their sensory system to acquire local and global cues about their surroundings. Previous research on tethered insects has suggested that in addition to vision and bending of cephalic bristles, insects use antennal mechanosensory feedback to maintain their airspeeds. Due to large displacement of migratory insects and the difficulties inherent in tracking single individuals, the roles of these sensory inputs have never been tested in freely migrating insects. We tracked individual uraniid moths (Urania fulgens) as they migrated diurnally over the Panama Canal and measured airspeed and orientation of individuals with either intact or amputated flagella. Consistent with prior observations that antennal input is necessary for flight control, more than half (59%) of the moths could not fly after flagellar amputation. The remaining fraction (41%) was flight-capable and maintained their prior airspeeds despite severe reduction in mechanosensory input from their antennae. Thus, airspeed maintenance may not involve antennal input alone, and is likely mediated by other modalities. Moths with amputated flagella could not recover their proper migratory orientation, suggesting that antennal integrity is necessary for long-distance navigation.