Phototactic behavior of Bemisia argentifolii (Homoptera: Aleyrodidae) crawlers

Abstract

First instars (crawlers) of Bemisia argentifolii Bellows & Perring were observed in the field and laboratory to move upward on plants, presumably in search of acceptable feeding sites. Laboratory experiments were conducted on a host plant and an artificial surface to determine if this movement was random, or a response to light (phototaxis) or gravity (geotaxis). Greenhouse-reared B. argentifolii crawlers were positively phototactic in experiments conducted on a host plant and on an artificial surface of black construction paper. Crawlers moved up or down the petiole of cheeseweed, Malva parviflora L., with equal facility, toward a light source placed either above or below the leaf blade. Response was always toward the light (positive phototaxis) and there was no response to gravity, either positive or negative. Crawlers placed on an artificial surface in a dark arena and presented with a point light source had a significant mean angular dispersion toward the light. Crawlers illuminated with uniform overhead lighting or kept in darkness moved about the arena at random. Crawlers maintained in darkness on cheeseweed and the artificial surface moved a significantly shorter distance from their origin than did those exposed to light. Such behavior suggests that some minimal light intensity may be necessary to stimulate crawler activity. The positive phototactic response may contribute to survival of B. argentifolii by enabling individuals eclosing from fall laid eggs, on leaves that become senescent during the winter, to find suitable leaves for development higher on the plant.