Characterising the variables associated with Tribolium castaneum adults that initiate flight in laboratory tests – Generating predictions for the field

Abstract

The flight behaviour of Tribolium castaneum was studied in the laboratory by characterising the physiological factors related to flight initiation in these small but long-lived beetles. We investigated the flight propensity of T. castaneum at two different ages at the same time: old beetles (∼12 weeks post-emergence) and young ones (∼2 weeks post-emergence). A mixture of old and young individuals was used as an independent test of whether flying beetles had the same characteristics as young beetles and residents the same ones as old. First generation laboratory cultures of field-collected beetles were used to avoid the known effects of protracted laboratory culturing. Beetles that initiated flight were captured individually in the laboratory using a customized trap, and their age, sex, weight, size, fat content, fecundity, and lipofuscin intensity (as a potential correlation of age) were determined. Beetles that had not flown in the test were simultaneously collected to represent residents (non-flyers) in each treatment. The assays indicated that flight propensity declined significantly with age (more young beetles flew than old ones), was not related to sex or weight, but was associated with size (larger beetles flew more). Lipofuscin intensity of old beetles was similar to that of young beetles, so is not a good indicator of age, but it was significantly higher in young flying females than young resident ones, so may be related to metabolic status. Fecundity assessments on a subset of the captured beetles indicate that total fecundity was not related to age or flight propensity. Based on these results we predict that most of the flying T. castaneum in the field will be relatively young beetles of high fat content. These individuals are likely to live longer than older beetles although the fecundity of females will not be higher. © 2018 Elsevier Ltd