Sex and Body Colour Affect the Variation in Internal Body Temperature of Oedaleus decorus asiaticus in Natural Habitats in Inner Mongolia, China

Abstract

Oedaleus decorus asiaticus is one of the most harmful locusts in agricultural and pastoral areas in China. Plagues of this grasshopper can aggravate grassland degradation and cause huge damage to the livestock industry. Fungal biopesticides are seen as a suitable means of controlling grasshoppers and locusts. However, the efficiency of fungal biopesticides is dependent on temperature. Currently, there is limited knowledge on the thermal biology of this grasshopper in natural habitats. In this study, ground temperature measurements were made in conjunction with measurements of internal body temperatures using thermocouples and hand-held thermometers. The grasshoppers were randomly caught during the daytime in 2017 and 2018 in eight different locations in Inner Mongolia Autonomous Region, China. Our results indicated that the average internal body temperature of nymphs as well as adults of O. d. asiaticusis was higher than the ground temperature and that it increases/decreases with increases/decreases in ground temperature, respectively, during the daytime. Moreover, the adult internal body temperature is significantly higher than that of the nymphs at different times of the day, specifically around 6:00, 10:00, 13:00, and 18:00. Female internal body temperatures were significantly higher than those of the males by an average of 0.90 °C. Additionally, the average internal body temperature of the brown morphs was higher than that of the green morphs by approximately 1.17 °C. These findings demonstrate that brown morph insects might be more tolerant of fungal biopesticides and hence the biopesticides may take longer to kill them. Hence, ecophysiological adaptations to climate change may affect how fungal biopesticides could be used in the future.