Passive aerodynamic stabilization by beetle elytra (wing covers)

Abstract

Summary. Most beetles extend their elytra laterally during flight, where they can act as fixed airfoils; typically, such elytra are held at a pronounced dihedral angle. We fixed extended elytra of June beetles (Scarabaeidae: Melolonthinae) and tiger beetles (Cicindelidae) over a range of dihedral angles (‐10° to 45°) and towed them in a water tunnel. We also towed them with flexed elytra (i.e. in the resting position). (Reynolds number was used to maintain dynamic similarity with air.) We measured the maximum rolling angle and the lateral oscillation rate as two indices of stability. There was no relationship between oscillation rate and dihedral angle, or between maximum roll angle and dihedral angle. At all dihedral angles tested, however, beetles were much more stable than when they were towed with the elytra flexed. We also included a third beetle type, flower beetle (Scarabaeidae: Cetoniine), which normally flies with flexed elytra. We measured stability indices for these beetles with elytra only in the flexed position. When all beetles were tested with flexed elytra, flower beetles showed no difference in maximum roll angle, but more stability in oscillation rate than the other two beetle types.

Dispersal differences of a pest and a protected Cerambyx species (Coleoptera: Cerambycidae) in oak open woodlands: a mark–recapture comparative study

“…Another important question is why Cc tends to fly more than Cw with faster wind speeds. We hypothesise that the distinct body shape between both species and the apparently better aerodynamic features of Cc (sharper body/elytra and more convex elytral section especially in the disk) could improve boost lift and flight efficiency in windy conditions (De Souza & Alexander, 1997;Sane, 2003;Johansson et al, 2012), an aspect that merits further research.…”

Ribosomal protein genes of holometabolan insects reject the Halteria, instead revealing a close affinity of Strepsiptera with Coleoptera

“…However, while direct experimentation on the modified forewings of Strepsiptera in a wind tunnel have shown they behave in a functionally similar way to dipteran halteres, the insights on lymexylid forewings are simply speculative (Pix et al, 1993). More commonly, Coleoptera forewings act as passive stabilizers (De Souza and Alexander, 1997). A more defensible example comes from male coccoid Hemiptera (Coccoidea), where hindwings are modified to 'hamulohalteres', anatomically similar to true hindwing halteres of Diptera, but undoubtedly their similarities are due to parallel evolution.…”

Robotic Elytra: Insect-Inspired Protective Wings for Resilient and Multi-Modal Drones

“…In nature, beetles use their elytra to achieve multiple goals beyond collision resilience. For example, camouflage [31], thermoregulation [13], humidity control [13], control through passive flight stability [32], and radiation control [33] according to the physical or chemical properties of the elytra. We also believe that with structural and chemical adaptation, it is possible to integrate further capabilities in the elytra to enable future robots to perform multiple other functionalities that are similar to what the Coleoptera have utilised to survive for millions of years in challenging and hazardous environments.…”