Odor tracking flight of male Manduca sexta moths along plumes of different cross-sectional area

Abstract

Males of the hawkmoth, Manduca sexta, track wind-borne plumes of female sex pheromone by flying upwind, while continuously turning from side-to-side and changing altitude. Their characteristic "zigzagging" trajectory has long been thought to result from the interaction of two mechanisms, an odor-modulated orientation to wind and a built-in central nervous system turning program. An interesting and as of yet unanswered question about this tracking behavior is how the cross-section of an odor plume or its clean-air "edges" affects moths' odor tracking behavior. This study attempts to address this question by video recording and analyzing the behavior of freely flying M. sexta males tracking plumes from pheromone sources of different lengths and orientations with equal odor concentration per unit area. Our results showed that moths generated significantly wider tracks in wide plumes from the longest horizontally-oriented sources as compared to narrower point-source plumes, but had relatively unaltered tracks when orienting to plumes from the same length sources oriented vertically. This suggests that in addition to wind and the presence of pheromones, the area of the plume's cross section or its edges may also play an important role in the plume tracking mechanisms of M. sexta.

Plume-Tracking Behavior of Flying Drosophila Emerges from a Set of Distinct Sensory-Motor Reflexes

“…To explain this behavior, Kennedy and Marsh proposed that casting is controlled by an internal clock, which is temporarily suppressed at the onset of odor [4,7,21]. Recent evidence, however, suggests that moths' casting dynamics are not simply a function of an internal clock, but rather that plume dynamics influence the amplitude of their casts [39]. An alternative to the internal clock mechanism is that moths exhibit the same simpler stigmergic iteration that we propose for flies and that their casting maneuvers in homogenous plumes are explained by a perceptual loss of the plume due to sensory adaptation, a phenomenon that is consistent with some experimental studies [40].…”

One antenna, two antennae, big antennae, small: total antennae length, not bilateral symmetry, predicts odor tracking performance in the American cockroach, Periplaneta americana L

“…The transition from odor plume to clean air at the lateral edge typically occurs within ca. 1 cm (Willis et al, 2013; see also plume measurements in this study in Materials and methods, below). In support of this idea, it is noteworthy that the narrowest tracks generated by P.…”

“…2) was determined using an electroantennogram preparation, similar to previous work in our lab (Willis et al, 2013;Talley, 2010). Because P. americana antennae are too slender to accept a fine silver wire into their lumen, we placed them between saline-filled capillaries, connected to silver-wire electrodes.…”

Olfactory coding in the turbulent realm

“…However, opposite to vertebrates the insect nose is everted and can continuously monitor odor stimuli whose temporal structure is not distorted by respiratory cycles [18][19][20][21] and differential sorption into the mucus layer of the olfactory epithelium [22][23][24][25]. The rapid responses and rich dictionary of maneuvers of moths in turbulent flows suggest efficient coding of olfactory plume dynamics [26]. In turbulent environments, the flight is empirically described by two dynamical behavioral features: upwind surge, associated to pheromone perception, and zigzagging, a cast maneuver to retrieve odor plumes when lost [27][28][29].…”