Seasonal Dynamics of Red Imported Fire Ant (Solenopsis invicta) Colony Structures Across Camellia oleifera Plantations and Fishponds in South China

The red imported fire ant (<i>Solenopsis invicta</i>, RIFA) is a globally invasive species with strong sensitivity to environmental conditions. This study investigated the seasonal dynamics and colony structure of RIFA over the course of one year across two typical habitats in South China: <i>Camellia oleifera</i> plantations and fishponds. The results revealed clear seasonal patterns in caste composition. Worker abundance peaked during winter (December-January), while reproductive individuals (queens, males, and alates) emerged primarily in spring and early summer (March-May). Colony biomass, worker number, and individual dry weight were significantly higher in <i>C. oleifera</i> plantations, whereas fishpond habitats exhibited greater numbers of larvae and male alates, suggesting different reproductive allocation strategies across habitats. An analysis of caste composition indicated that adult workers were dominant in both habitats, but the proportion of pupae was notably higher in fishpond colonies, especially in spring. Significant correlations were found between colony metrics and nest characteristics, including a negative relationship between worker body length and colony biomass. Environmental factor analysis showed that air pressure positively influenced worker numbers, while temperature was negatively associated with them. Precipitation and humidity played key roles in regulating larval and pupal populations. Overall, <i>RIFA</i> exhibited strong seasonal patterns and ecological plasticity in response to habitat differences and environmental variables. These findings provide insights into the species' invasion biology and inform habitat-specific monitoring and management strategies.