Postdiapause Development and Hatching Rate of Three Grasshopper Species (Orthoptera: Acrididae) in Inner Mongolia

Abstract

The postdiapause development, hatching characteristics, and survival of the overwintering eggs of the grasshopper species Oedaleus asiaticus Bei-Bienko, Angaracris barabensis (Pallas), and Chorthippus dubius (Zubowsky) from the Inner Mogolian steppe grasslands were studied at six constant temperatures (15, 20, 25, 30, 35, and 40°C). The results show that the three species had different postdiapause embryonic developmental rates, survival curves, and cumulative hatching probabilities. O. asiaticus had the highest developmental threshold at 13.1°C and the least effective accumulated thermal unit, 191.7 degree-days (DD). A. barabensis had the lowest developmental threshold at 11.1°C and the most effective accumulated thermal unit, 329.7 DD. C. dubius, a later hatching species, had a moderate developmental threshold of 11.4°C and an effective accumulated thermal unit of 230.3 DD. The effective thermal unit at which 50% of postdiapause eggs hatched was 202.7 DD for O. asiaticus, 340.8 DD for A. barabensis, and 251.6 DD for C. dubius. The greatest percentage hatch of O. asiaticus (71.06%), A. barabensis (75.28%), and C. dubius (87%) occurred at 27.3, 27.8, and 27.4°C, respectively. Thermal death points of the three grasshopper species were 41.0°C, 40.5, and 44.8°C, respectively. The optimal temperature ranges of each species were different, 21.9 to 32.7°C for O. asiaticus, 22.0 to 33.5°C for A. barabensis, and 17.8 to 37.1°C for C. dubius. These results suggest that postdiapause embryonic developmental rate and accumulated heat cannot help to explain the different hatching sequences of these species. Much variation in springtime emergence could be attributed to the species-specific overwintering egg stage. In addition, results also indicate that C. dubius has a wider adaptive temperature range than O. asiaticus and A. barabensis.