The descent of ant: field-measured performance of gliding ants

Abstract

Gliding ants avoid predatory attacks and potentially mortal consequences of dislodgement from rainforest canopy substrates by directing their aerial descent towards nearby tree trunks. The ecologically relevant measure of performance for gliding ants is the ratio of net horizontal to vertical distance traveled over the course of a gliding trajectory, or glide index. To study variation in glide index, we measured three-dimensional trajectories of Cephalotes atratus ants gliding in natural rainforest habitats. We determined that righting phase duration, glide angle, and path directness all significantly influence variation in glide index. Unsuccessful landing attempts result in the ant bouncing off its target and being forced to make a second landing attempt. Our results indicate that ants are not passive gliders and that they exert active control over the aerodynamic forces they experience during their descent, despite their apparent lack of specialized control surfaces.

Arachnid aloft: directed aerial descent in neotropical canopy spiders

“…Inferred control motions of the forelegs in gliding would benefit from detailed kinematic studies of leg and body orientations during manoeuvres. Similarly, three-dimensional trajectory reconstruction under field conditions would enable descent velocities and manoeuvres to be quantified for comparison with existing data on gliding ants [20]. The relatively high body moment of inertia for these spiders in yaw, and relatively small forces associated with their small legs, may yield somewhat imprecise control.…”

Shifts in stability and control effectiveness during evolution of Paraves support aerial maneuvering hypotheses for flight origin

“…To explore parallel evolution and for calibration, we also constructed models of three pterosaurs, two bats, and two artificial test objects (sphere and weather vane) (Figure 2). Construction methods closely followed those of (Koehl et al, 2011; Evangelista et al, 2014b; Evangelista, 2013; Munk, 2011; Zeng, 2013). Solid models were developed in 95 Blender (The Blender Foundation, Amsterdam), closely referencing published photographs of fossils and reconstructions from the peer-reviewed literature and casts of Archaeopteryx to match long bone, axial skeleton, and body proportions.…”

“…Model construction. Models were developed in Blender (a) from fossils (Archaeopteryx shown) and constructed using previous methods (McCay, 2001; Koehl et al, 2011; Munk, 2011; Evangelista et al, 2014b). Models for fossil paravians studied are shown in (b-h), scale bars indicate 8 cm snout-vent length.…”

“…Regardless of how aerial behavior originates, once airborne an organism must control (Smith, 1952) its orientation and position in order to safely navigate the vertical environment (e.g., directed aerial descent, Dudley and Yanoviak, 2011). Such abilities are present even in taxa with no obvious morphological adaptation for flight (such as Cephalotes ants, Munk, 2011; geckoes, Jusufi et al, 2008, Jusufi et al 2011; stick insects, Zeng, 2013; and human skydivers, Cardona et al, 2011; Evangelista et al, 2012). At low speeds, such as at the start of a fall or jump, inertial mechanisms (Jusufi et al, 2008, Jusufi et al2011) allow for rolling, pitching, and yawing.…”

The visual ecology of directed aerial descent in first-instar nymphs of the stick insectExtatosoma tiaratum

“…whether to hide or remain exposed after landing. Given the diverse types of forest canopies (Erwin, 1988) and independent evolution of DAD in many different taxa Munk et al, 2015), other mechanisms of visual guidance likely remain to be documented. For instance, preliminary experiments in other nymphal and adult stick insects have shown DAD landing unassociated with visual contrast (e.g.…”