title: Visual ecology of directed aerial descent in first-instar nymphs of the stick insect Extatosoma 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 well-defined 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.
authors.affiliation: Department of Integrative Biology, University of California, Berkeley, CA 94720, USA dreavoniz@berkeley.edu.
authors.forename: Yu
authors.initials: Y
authors.lastname: Zeng
authors.affiliation: Department of Integrative Biology, University of California, Berkeley, CA 94720, USA.
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Lin
authors.affiliation: Department of Integrative Biology, University of California, Berkeley, CA 94720, USA.
authors.forename: Arianna
authors.initials: A
authors.lastname: Abundo
authors.affiliation: Department of Integrative Biology, University of California, Berkeley, CA 94720, USA Smithsonian Tropical Research Institute, Balboa, Republic of Panama.
authors.forename: Robert
authors.initials: R
authors.lastname: Dudley
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D003116:Color; D003463:Cues; D007313:Insecta / Q000502:physiology*; D008124:Locomotion; D009758:Nymph / Q000502:physiology; D014785:Vision, Ocular
keywords: Canopy; Gliding; Invertebrate; Vision