Visual Ability and Searching Behavior of Adult Laricobius nigrinus, a Hemlock Woolly Adelgid Predator

Very little is known about the searching behavior and sensory cues that Laricobius spp. (Coleoptera: Derodontidae) predators use to locate suitable habitats and prey, which limits our ability to collect and monitor them for classical biological control of adelgids (Hemiptera: Adelgidae). The aim of this study was to examine the visual ability and the searching behavior of newly emerged L. nigrinus Fender, a host-specific predator of the hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Phylloxeroidea: Adelgidae). In a laboratory bioassay, individual adults attempting to locate an uninfested eastern hemlock seedling under either light or dark conditions were observed in an arena. In another bioassay, individual adults searching for prey on hemlock seedlings (infested or uninfested) were continuously video-recorded. Beetles located and began climbing the seedling stem in light significantly more than in dark, indicating that vision is an important sensory modality. Our primary finding was that searching behavior of L. nigrinus, as in most species, was related to food abundance. Beetles did not fly in the presence of high A. tsugae densities and flew when A. tsugae was absent, which agrees with observed aggregations of beetles on heavily infested trees in the field. At close range of prey, slow crawling and frequent turning suggest the use of non-visual cues such as olfaction and contact chemoreception. Based on the beetles' visual ability to locate tree stems and their climbing behavior, a bole trap may be an effective collection and monitoring tool

The developmental cycle of domestic groups and Amazonian deforestation

It has been common to attribute tropical deforestation to population growth and/or migration. This paper finds that this is true only at large and aggregated spatial and temporal scales. When one examines regional-scaled processes, there are numberous mediating factors and more complex demographic processes that account for differences in rates of deforestation. Based upon three years of research in the Altamira region, Xingu Basin, Brazilian Amazon, we differenttiate between period and cohort effects in trajectories of deforestation. We find that every cohort of migrants follows the same overall trajectory of deforestation but that the magnitude of deforestation along a 20 year trajectory is dependent on period effects (such as hyperinflation, credit policy, land policy changes). Moreover, we find that the 20-year trajectory does indeed follow the constraints posed by the development cycle of the domestic group-refleting as it does the changing supply of labor