Effect of Water Immersion on Workers Mortality of the Imported Fire Ant, Solenopsis invicta (Hymenoptera: Formicidae)

Author of the article:YU Yu-Ting, CHEN Li, WEI Hong-Yi

Author's Workplace：College of Agronomy, Jiangxi Agricultural UniversityState Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences

Key Words：Solenopsis invicta, worker, water immersion, temperature, mortality

Abstract：Flooding could put terrestrial organisms, especially soil insects, in hypoxia conditions. The red imported fire ants, Solenopsis invicta Buren always build their nests in humid areas, which makes them being immersed by flooding at a high risk. We studied the effects of immersion time and temperature on workers of the imported fire ant in the laboratory. The workers mortality was influenced significantly by the time that the workers were immersed in water. The longer the immersion time was, the higher the workers mortality would be. The relationship between the immersion time (T) and mortality (M) is in accordance with the following model: Mminor = -25.01 + 4.49T for minor workers; Mmajor = -26.9 + 3.96T for major workers. And the major workers have stronger immersion tolerance than the minor workers. Temperature also plays an important role in the minor workers mortality after immersion. The minor workers mortality after 10 h immersion was obtained at seven different temperatures (5, 10, 15, 20, 25, 30 and 35 ℃). And the correlation of mortality and temperature of the minor workers matches the mathematical second order polynomial regression model : Y = 115.2 - 11.88 X + 0.33 X2. And when X = 18.21 ℃, the equation has the minimum value Y = 7.04%.