Rates of metabolism in diapausing and reproductively active tropical butterflies, Euploea core and Euploea sylvester (Lepidoptera: Nymphalidae)

Abstract

Although the ecology of diapause has been widely studied in the field, the underlying physiological responses occurring in tropical diapausing insects remain virtually unexplored. This is especially the case with rates of respiration in diapausing tropical insect species. The present study compares rates of metabolism, as assessed by measurement of carbon dioxide production, between two species of diapausing and reproductively active tropical butterflies, Euploea core (W.S Macleay) and Euploea sylvester (Fabricius), independent of temperature. Measurement of metabolism over a day-time/night-time regime confirms that these tropical butterflies display a diurnal rhythm in accordance with many other tropical and temperate insect species, regardless of developmental state. In addition, diapausing Euploea butterflies display rates of carbon dioxide production only 28% lower than those of reproductively active butterflies, and can terminate diapause within days of receiving the correct cues. Maintaining a similar metabolic rate throughout diapause, as well as a rapid termination of diapause, would enable these tropical butterflies to respond immediately to larval host plant resources, without the disadvantage of missing optimum conditions, allowing the species to maximize their reproductive potential.