Living in a trash can: turbulent convective flows impairDrosophilaflight performance

Abstract

Turbulent flows associated with thermal convection are common in areas where the ground is heated by solar radiation, fermentation or other processes. However, it is unknown how these flow instabilities affect the locomotion of small insects, like fruit flies, that inhabit deserts and urban landscapes where surface temperatures can reach extreme values. We quantified flight performance of fruit flies ( Drosophila melanogaster ) traversing a chamber through still air and turbulent Rayleigh–Bénard convection cells produced by a vertical temperature gradient. A total of 34% of individuals were unable to reach the end of the chamber in convection, although peak flow speeds were modest relative to typical outdoor airflow. Individuals that were successful in convection were faster fliers and had larger wing areas than those that failed. All flies displayed higher pitch angles and lower mean flight speeds in convection. Successful individuals took longer to cross the chamber in convection, due to lower flight speeds and greater path sinuosity. All individuals displayed higher flapping frequencies in convection, and successful individuals also reduced stroke amplitude. Our results suggest that thermal convection poses a significant challenge for small fliers, resulting in increased travel times and energetic costs, or in some cases precluding insects from traversing these environments entirely.

Kinematic flexibility allows bumblebees to increase energetic efficiency when carrying heavy loads

“…Enhancing translational lift forces by increasing flapping frequency is expensive, so there is presumably some benefit to using a higher wingbeat frequency when energetic efficiency is not critical. Several recent studies on flight performance in unsteady flow environments show that a number of insects, including moths (33), fruit flies (34), and bumblebees (35), increase flapping frequency when flying in external flow conditions that challenge their stability. Higher flapping frequencies have been proposed to enhance stability by several potential mechanisms, such as reducing the impact of random, turbulent flow perturbations on force production by flapping wings (36) or damping out rotational perturbations via flapping countertorque (37).…”

Honeybees modify flight trajectories in turbulent wind

“…The study of insect flight has gathered much interest due to their relative ease of handling and performing controlled laboratory experiments in different environments, such as the study of fruit flies [10,11] and midges [12]. Particular insects of interest have been the honeybee, bumblebee and orchid bee since they are vital to the environment as natural pollinators [13,14].…”

Natural barriers: waterfall transit by small flying animals

“…0.5 cm, mass of 20 mg), travel with sufficient energy per cross-sectional area (162 × 10 −3 J m −2) , to easily break the surface tension. Fruit flies moving here at 0.6 m s −1 (or even at maximum speeds of 1.1 m s −1 [ 14 ]), generated kinetic energy per unit area equal to 0.33–1 σ , and thus could not break through the moving water sheet. Insects such as craneflies experience even greater difficulties, as penetration is initiated by deformable legs or antennae which remain attached to the moving water and result in substantial torque and downward entrainment of the body.…”