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

Abstract

Many wingless insects perform directed aerial descent (DAD) to return to vegetational structures after falling. Given the complex visual environment and spatial structures of tree canopies, those visual signals used as directional cues are not fully understood. Here, we address the role of visual contrast for DAD in newly hatched nymphs of the stick insect Extatosoma tiaratum under controlled laboratory conditions. Landing preferences of gliding E. tiaratum in various visual environments were studied. We used a single vertical stripe defined by variable contrast edges to test the use of contrast consistency and sharpness. We also used aggregate patterns to examine the effects of target size and the effectiveness of luminance contrast and chromatic contrast. E. tiaratum nymphs were attracted to single stripes with welldefined edges, and particularly favored narrow dark targets. The directionality and accuracy of landing were dependent on target size. Lastly, luminance contrasts were more effective in attracting landings than were chromatic contrasts. Visual contrasts are therefore used as spatial references for landing behavior in DAD. These behaviors may enable nymphs to quickly locate dark or shaded sides of vertically oriented vegetation in natural habitats.

How does a slender tibia resist buckling? The effect of material, structural and geometric characteristics on the buckling behaviour of the hindleg tibia in the postembryonic development of the stick insectCarausius morosus

“…A recent study reported frequent intentional drops or accidental falls of the wingless stick insect Extatosoma tiaratum, while climbing vegetation (Zeng et al, 2015). This behaviour, which may serve as a defence reaction, is also likely to be valid for the wingless species C. morosus.…”

Many ways to stick the landing: novel righting strategies allow spotted lanternfly nymphs to land on diverse substrates

“…Glue was applied so as to avoid coating the feet, which still adhered to substrates after being glued. Following previous studies (Ribak et al, 2013;Zeng et al, 2015;Meresman, Ben-Ari and Inbar, 2017), we released specimens with the goal of achieving low initial speed and spin while controlling initial falling orientation. Live and dead specimens were released using featherweight entomology tweezers (DRENTF01, DR Instruments, Palos Hills, IL US) (Fig.…”

Dropping to escape: a review of an under‐appreciated antipredator defence

“…Classical gliding in terrestrial vertebrates was likely an important precursor to the evolution of powered flight (Dudley et al, ; Dudley & Yanoviak, ). Directed aerial descent has only fairly recently been described in a variety of wingless arboreal insects too (Yanoviak, Dudley & Kaspari, ; Yanoviak, Fisher & Alonso, ; Yanoviak, Munk & Dudley, , ; Zeng et al, ). It is important to note here that, while dropping from the air and directed aerial descent fall under our definition of dropping, those species such as flying squirrels that have extensive morphological adaptation for gliding used for routine movement through the environment as well as escape from predators are best seen as a separate phenomenon.…”

“…When not being used to escape enemies, voluntarily falling is sometimes deployed by invertebrates as a shortcut to the ground or to access high-quality food patches (Haemig, 1997;Ohzora & Yano, 2011). In fact, more controlled dropping behaviour -known as 'directed falling' or directed aerial descent -has been reported in a number of wingless ant species (Yanoviak et al, 2005(Yanoviak et al, , 2008(Yanoviak et al, , 2010Yanoviak & Dudley, 2006) as well as spiders (Yanoviak et al, 2015) and stick insects (Zeng et al, 2015). Directed aerial descent is considered a form of gliding, but it occurs at steeper angles than 'classical gliding' (Dudley et al, 2007).…”