Aerial manoeuvrability in wingless gliding ants (Cephalotes atratus)

Abstract

In contrast to the patagial membranes of gliding vertebrates, the aerodynamic surfaces used by falling wingless ants to direct their aerial descent are unknown. We conducted ablation experiments to assess the relative contributions of the hindlegs, midlegs and gaster to gliding success in workers of the Neotropical arboreal ant Cephalotes atratus (Hymenoptera: Formicidae). Removal of hindlegs significantly reduced the success rate of directed aerial descent as well as the glide index for successful flights. Removal of the gaster alone did not significantly alter performance relative to controls. Equilibrium glide angles during successful targeting to vertical columns were statistically equivalent between control ants and ants with either the gaster or the hindlegs removed. High-speed video recordings suggested possible use of bilaterally asymmetric motions of the hindlegs to effect body rotations about the vertical axis during targeting manoeuvre. Overall, the control of gliding flight was remarkably robust to dramatic anatomical perturbations, suggesting effective control mechanisms in the face of adverse initial conditions (e.g. falling upside down), variable targeting decisions and turbulent wind gusts during flight.

Touchdown to take-off: at the interface of flight and surface locomotion

“…As a result, these animals typically approach a landing target at relatively higher speeds than powered flyers do. Gliders that use their limbs and body to direct their descent include many arthropods, such as some spiders and wingless hexapods [90][91][92][93][94]. Gliding vertebrates, including flying squirrels, colugos, snakes, lizards and frogs, use their extended aerodynamic surfaces to navigate in the air [71,[74][75][76][77][78][79].…”

Arachnid aloft: directed aerial descent in neotropical canopy spiders

“…To avoid these problems, workers of many ant species, and many other wingless hexapods, orient their falls towards tree trunks upon which they land [4][5][6]. Using visual cues [7] and either appendages or axial structures to manoeuvre [5,8], these taxa generate both lift and drag on the body to glide at steep angles in the behaviour we have termed directed aerial descent [4]. The capacity of wingless species or morphs to control their glide trajectory, along with an initial aerial righting reflex, have important implications for our understanding of the origins of animal flight [9].…”

“…The rates of change in body heading were then correlated with values for the simultaneous left/right differences in foreleg angle for each individual sequence, and then for all pooled data. Although these estimates only represent projected body and appendage angles within the horizontal plane, and do not necessarily correspond to similar dynamic states among individual spiders, they can nonetheless identify, in part, those control mechanisms underlying changes in body orientation [8].…”

Biomechanics of aerial righting in wingless nymphal stick insects

“…For example, wingless Cephalotes ant workers rapidly swing their legs for control during directed aerial descent, with angular limb speeds exceeding 1508 s 21 [12]). Comparable studies of aerial manoeuvring among arthropod species of different morphologies (e.g.…”

“…For example, small aphids elevate their legs dorsally to effect an aerodynamically unstable profile during upside-down falls, enabling passive body rotation driven by aerodynamic torque [11,12]. In addition to passive aerodynamic righting initiated by reflex actions followed by a constant leg posture, more actively controlled appendicular movements are also feasible.…”