Meeting Abstract
P1.163 Sunday, Jan. 4 Optical geometry, perch orientation, and microhabitat selection in a sit-and-wait aerial predator, Megalagrion xanthomelas WALGUARNERY, J.*; SCHROEDER, R.; BUTLER, M.A.; University of Hawaii; University of Hawaii; University of Hawaii justinww@hawaii.edu
Habitats of high spatial variation in absolute light levels and spectral quality present a challenge to animals that rely on visual orientation and visual target discrimination. Insects, in particular, have several factors working against consistent visual performance in complex environments including the lack of a focusing mechanism, relatively limited light capture and coarse spatial resolution of their compound eyes. Therefore, an understanding of the morphological and behavioral means by which insects overcome these limitations in order to perform highly demanding visual tasks is important both to questions of habitat specialization and visual system optimization. We investigated optical geometry, perch orientation and microhabitat selection in the Hawaiian damselfly Megalagrion xanthomelas, a sit-and-wait predator that intercepts aerial prey among heterogeneous vegetation bordering streams and wetlands. We found that while the eyes of M. xanthomelas are roughly spherical, visual acuity appears concentrated in a region located approximately 15 degrees below the equatorial frontal plane. This optical geometry corresponds with typical orientations of damselflies resting on perches and suggests an arrangement maximizing detection of prey or conspecifics traveling along stream margins. Although available optical microhabitats differed widely, overall variation and microhabitat selection could be largely described by single synthetic variables summarizing total photon flux and relative levels of ultraviolet and infrared irradiance. We discuss the extension of this research to the development of explicit evolutionary hypotheses and the use of the diverse, endemic Hawaiian damselfly genus Megalagrion as a model system for examination of selective pressures shaping the visual system and influencing visual ecology.
