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ABSTRACT Foraging insects fly over long distances through complex aerial environments, and many can maintain constant ground speeds in wind, allowing them to gauge flight distance. Although insects encounter winds from all directions in the wild, most lab-based studies have employed still air or headwinds (i.e. upwind flight); additionally, insects are typically compelled to fly in a single, fixed environment, so we know little about their preferences for different flight conditions. We used automated video collection and analysis methods and a two-choice flight tunnel paradigm to examine thousands of foraging flights performed by hundreds of bumblebees flying upwind and downwind. In contrast to the preference for flying with a tailwind (i.e. downwind) displayed by migrating insects, we found that bees prefer to fly upwind. Bees maintained constant ground speeds when flying upwind or downwind in flow velocities from 0 to 2 m s−1 by adjusting their body angle, pitching down to raise their air speed above flow velocity when flying upwind, and pitching up to slow down to negative air speeds (flying backwards relative to the flow) when flying downwind. Bees flying downwind displayed higher variability in body angle, air speed and ground speed. Taken together, bees' preference for upwind flight and their increased kinematic variability when flying downwind suggest that tailwinds may impose a significant, underexplored flight challenge to bees. Our study demonstrates the types of questions that can be addressed with newer approaches to biomechanics research; by allowing bees to choose the conditions they prefer to traverse and automating filming and analysis to examine massive amounts of data, we were able to identify significant patterns emerging from variable locomotory behaviors, and gain valuable insight into the biomechanics of flight in natural environments.
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Close encounters of three kinds: impacts of leg, wing and body collisions on flight performance in carpenter bees
Flying insects often forage among cluttered vegetation that forms a series of obstacles in their flight path. Recent studies have focused on behaviors needed to navigate clutter while avoiding all physical contact and, as a result, we know little about flight behaviors that do involve encounters with obstacles. Here, we challenged carpenter bees (Xylocopa varipuncta) to fly through narrow gaps in an obstacle course to determine the kinds of obstacle encounters they experience, as well as the consequences for flight performance. We observed three kinds of encounters: leg, body and wing collisions. Wing collisions occurred most frequently (in about 40% of flights, up to 25 times per flight) but these had little effect on flight speed or body orientation. In contrast, body and leg collisions, which each occurred in about 20% of flights (1–2 times per flight), resulted in decreased flight speeds and increased rates of body rotation (yaw). Wing and body collisions, but not leg collisions, were more likely to occur in wind versus still air. Thus, physical encounters with obstacles may be a frequent occurrence for insects flying in some environments, and the immediate effects of these encounters on flight performance depend on the body part involved.
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- Award ID(s):
- 1856752
- PAR ID:
- 10557021
- Publisher / Repository:
- Company of Biologists
- Date Published:
- Journal Name:
- Journal of Experimental Biology
- Volume:
- 226
- Issue:
- 9
- ISSN:
- 0022-0949
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Flying insects are equipped with complex olfactory systems, which they utilize to seek food, identify mates, and evade predators. It is suspected that insects flap their wings to draw odor plumes toward their antennae, a behavior akin to mammals' sniffing, aimed at enhancing olfactory sensitivity. However, insects' wing kinematics change drastically as their flight speed increases, and it is unknown how these changes affect the insect's odorant perception. Addressing this gap in knowledge is crucial to a full understanding of the interplay between insects' aerodynamic performance and sensory perception. To this end, we simulated odor-tracking hawkmoth flight at 2 and 4 m/s using an in-house computational fluid dynamics solver. This solver incorporated both the Navier–Stokes equations that govern the flow, as well as the advection-diffusion equation that governs the odor transport process. Findings indicate that hawkmoths enhance odor intensity along their antennae using their wings, with peak odor intensity being 39% higher during 2 m/s flight compared to 4 m/s flight. This demonstrates there is a trade-off between rapid transport and olfaction, which is attributable to differences in wing kinematics between low- and high-speed flights. Despite literature suggesting hawkmoths are limited to steady forward flights at speeds below 5 m/s—about half of what is theoretically predicted based on body mass—this study reveals that slower flight speeds improve their olfactory capabilities during navigation. Our findings offer insights into the evolution of flight and sensory capabilities in hawkmoths, as well as provide inspiration for the development of bio-inspired odor-guided navigation technologies.more » « less
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Animals that move through complex habitats must frequently contend with obstacles in their path. Humans and other highly cognitive vertebrates avoid collisions by perceiving the relationship between the layout of their surroundings and the properties of their own body profile and action capacity. It is unknown whether insects, which have much smaller brains, possess such abilities. We used bumblebees, which vary widely in body size and regularly forage in dense vegetation, to investigate whether flying insects consider their own size when interacting with their surroundings. Bumblebees trained to fly in a tunnel were sporadically presented with an obstructing wall containing a gap that varied in width. Bees successfully flew through narrow gaps, even those that were much smaller than their wingspans, by first performing lateral scanning (side-to-side flights) to visually assess the aperture. Bees then reoriented their in-flight posture (i.e., yaw or heading angle) while passing through, minimizing their projected frontal width and mitigating collisions; in extreme cases, bees flew entirely sideways through the gap. Both the time that bees spent scanning during their approach and the extent to which they reoriented themselves to pass through the gap were determined not by the absolute size of the gap, but by the size of the gap relative to each bee’s own wingspan. Our findings suggest that, similar to humans and other vertebrates, flying bumblebees perceive the affordance of their surroundings relative their body size and form to navigate safely through complex environments.more » « less
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1242/jeb.245334
