红火蚁自然种群耐寒性的研究

为综合评价红火蚁Solenopsis invicta Buren的抗寒能力, 依据2005-2006年在深圳野外获得的红火蚁自然种群测定了其不同品级及虫态的过冷却点和低温处理后的存活率。研究结果表明：红火蚁各品级及其3个虫态的过冷却点之间存在显著差异。工蚁与雌、雄有翅蚁之间的过冷却点不存在差异, 而雌、雄有翅蚁之间的过冷却点存在差异；不同虫态过冷却点大小依次为蛹﹤成虫﹤幼虫。红火蚁自然种群在越冬前后存在过冷却点波动的现象, 表现为从10月份开始红火蚁野外种群的过冷却点开始逐渐下降, 在2月份达到最低, 为-12.68℃, 3月份回升到-9.51℃。红火蚁低温下的存活率S^T与低温暴露温度T和暴露时间t之间的关系均符合逻辑斯谛曲线方程。当处理时间为0.5 h, 红火蚁在-14℃时存活率为15.3%；当处理时间为1, 2和4 h, 工蚁在处理温度分别为-13, -9和-9℃才可全部致死。当处理温度为-10℃, 需要经过240 min工蚁才全部死亡, 在-11℃, 则需要120 min。相同低温的不同变幅和持续作用对工蚁的存活有较大的影响。总体来说, 经过相同的处理时间, 低温变幅越大存活率越低, 而且存活率降至0所需要的时间也不同, 4±9℃处理时在经过9 d即降为0, 而4±0℃处理则要长于15 d。与对照相比, 4±6℃和4±9℃处理4 d能显著提高工蚁在低温下的存活率。结果提示，不同变幅的持续低温作用对红火蚁的抗寒能力有着驯化作用, 红火蚁对极端气候有较强的适应能力。

Cold hardiness of natural populations of the red imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae) in Shenzhen, Guangdong

To obtain a comprehensive evaluation of cold hardiness of the red imported fire ant, Solenopsis invicta Buren, the super cooling points ( SCPs) of different casts at developmental stages and the ability of workers to survive at low temperature were measured based on materials collected from S. invicta natural populations of Shenzhen, Guangdong in 2005 - 2006. The results showed that there was a significant difference in SCPs between casts and three developmental stages while the SCPs of the larva, adult and pupa reduced successively. No significant difference was found between the workers and the winged ants in SCPs, but significant difference existed between male and female winged ants. SCPs fluctuated over winter, reduced from October and got to the bottom ( - 12. 68℃ ) in February, and rose to -9. 51℃ in March.The survivorship of workers (S_T) showed a strong relationship with the exposure temperature ( T) and the exposure time (t), fitting the Logistic equation. When the exposure time was 0. 5 h, the survival rate of workers was 15. 3% at - 14℃. At the exposure time of 1, 2 and 4 h, the entire lethal temperatures for S. invicta were - 13℃ ,- 9℃ and -9℃, respectively. When the exposure temperature was -10℃, all workers died within 240 min; while at -11℃, it took only 120 min. Fluctuation and persistence of low-temperature were correlative with the survival rate of workers. Under more fluctuating low temperature, the workers had a higher mortality. It took 9 d for the survival rate to drop to 0 under the condition of 4 ±9℃ , while it was longer than 15 d for that under 4 ± 0℃. But the survivors grew stronger in cold tolerance. Compared with the control, treatments under fluctuating temperature of 4 ±6℃ and 4 ±9℃ for 4 d could raise the survived workers' cold tolerance at low temperature significantly. The results suggest that the fire ant can obtain rapid acclimatization when exposed to low temperatures, and it has strong adaptability to extreme weather.