›› 2009, Vol. 52 ›› Issue (5): 502-508.

• RESEARCH PAPERS • Previous Articles     Next Articles

Determination of the supercooling points of various castes and developmental stages of the red imported fire ant, Solenopsis invicta (Hymenoptera: Formicidae) in mainland China

  

  • Online:2009-05-20 Published:2009-05-20

Abstract: The red imported fire ant, Solenopsis invicta Buren, is a social insect pest found recently in mainland China. To elucidate the cold hardness and provide basis for its risk assessment in mainland China, the supercooling points (SCPs) of various castes and individuals of various developmental stages collected from different geographical locations, seasons and durative starvations treatment were examined. The results indicated that the SCPs of fire ants differed significantly among castes and developmental stages. The worker ants had significant lower SCPs (-11.8±0.4℃) than those of female alates (-8.1±0.6℃) and queens (-7.9±0.5℃). The SCPs of the pupae and larvae of workers and queens were -13.6±0.3, 12.1±0.4, 13.3±0.3 and 12.2±0.3℃, respectively. Worker pupae had lower SCPs than worker adults and worker pupae. There was no significant difference between queen larvae and its pupae. At the same immature stage, SCPs of various castes did not differ from each other. The SCPs were not significantly different in workers collected from different geographical locations of Luchuan, Guangzhou, Zhuhai and Shenzhen in spring, autumn and winter except those collected in summer, when workers in Luchuan had remarkable lower SCPs than other locations (P<0.05). SCPs of worker ants decreased as the season progressed, with the highest for spring (-4.3±0.2℃), the second for summer (-6.6±0.2℃), and third for autumn (-9.4±0.1℃) and lowest (-12.0±0.3℃) for winter colonies. The SCPs of worker ants increased greatly by a durative starvation for 15 d. The SCPs of major workers and minor workers increased 7.0℃ and 4.9℃, respectively during the starvation test, suggesting that the major workers are less resistant to starvations than the minor workers. These results will support theoretically for risk analysis of Solenopsis invicta potential disperse in China.

Key words: Solenopsis invicta, cold tolerance, supercooling point, castes, developmental stage, geographical colonies, season, starvation, China