Behaviour in the presence of resource excess—flight of Tribolium castaneum around heavily-infested grain storage facilities

Abstract

The flight of Tribolium castaneum (Herbst) in leaving infestations and establishing new infestations, independent of human mediation, has received little experimental attention. This study focuses on the patterns of flight of T. castaneum beetles in the nearby vicinity of an environment that provides all requirements—that is, an environment from which the beetles are not likely to be driven by density-related pressures. Four separate sampling strategies were implemented, with each one focused on particular sites in and around storage structures (godowns) in southern India. Additional beetles were sampled from each focus area of a storage facility at dusk to ascertain the allelic frequencies of resident and flying beetles at the rph2 gene which is partially responsible for resistance to the fumigant phosphine (PH₃). Results show that T. castaneum beetles clearly have a crepuscular flight pattern, with most flight occurring at dusk. Movement into and out of the facilities sampled evidently balanced one another, indicating that those beetles that initiated flight must eventually have returned to the same resource. Most beetles sampled from the bag stack surface during this crepuscular flight period were homozygous phosphine resistant at the rph2 locus (83.3%, n = 30). Conversely, most beetles caught in flight during the same period had at least one phosphine susceptible allele (86.7% above the back stack, 63.3% outside the godown n = 30 at each site). Explanations for the patterns observed are discussed, including resource abundance overriding dispersal flight, and the possible pleiotropic effects on flight propensity of phosphine resistance.