Population growth and development of the psocid Liposcelis obscura (Psocodea: Liposcelididae) at constant temperatures and relative humidities

Abstract

The effects of nine temperatures (22.5, 25.0, 27.5, 30.0, 32.5, 35.0, 37.5, 40.0, and 42.5 °C) and four relative humidities (RHs; 43, 55, 63, and 75%) on the population growth and development of the parthenogenetic Liposcelis obscura Broadhead (Psocodea: Liposcelididae) were investigated in laboratory studies. Results showed that L. obscura did not survive at 43% RH at all temperatures tested. At 55% RH, L. obscura survived at 22.5, 25, and 27.5 °C; none survived at 42.5 °C and ≤63% RH. Population growth was highest at 40.0 °C and 75% RH, where population increase was 216-fold from an initial population of five adult females. Liposcelis obscura has three-to-five nymphal instars, and the percentages of individuals with three, four, and five instars were 52, 41, and 7%, respectively. Temperature-dependent developmental equations were developed for L. obscura eggs, individual nymphal, combined nymphal, and combined immature stages. Liposcelis obscura populations grew much faster at 30–42.5 °C and 75% RH. Based on the equation for total developmental time, the predicted optimal development temperature is 39.2 °C and development was completed in 14.0 d. The upper developmental threshold was estimated as 47.1 °C. The lower developmental threshold was estimated as 14.7 °C. These data provide a better understanding of L. obscura population dynamics and can be used to develop effective management strategies for this psocid.