New methods for extracting and maintaining laboratory colonies of imported fire ants (IFA) have emerged, significantly improving the success of these colonies. Researchers from the USDA Agricultural Research Service (USDA-ARS) have developed and tested the moisture differential technique, which proves to be more effective than traditional water dripping methods.
Imported fire ants (Solenopsis invicta, S. richteri, and their hybrid forms) are formidable pests, impacting agricultural sectors and public health through painful bites. Established as invasive species, their adaptation has led to extensive infestations across the United States and beyond, underscoring the need for efficient laboratory study techniques to understand their behavior and biology.
The previous methods of colony extraction, primarily based on water dripping, have been effective over the years but come with significant downsides. According to the study, major mortality factors arise during extraction, leading to the loss of large portions of the colony including brood and queens. The new moisture differential technique addresses these shortcomings quite effectively.
This novel approach begins by drying the mound soil collected from the field. Ant colonies naturally seek moist environments to avoid dehydration, so during the drying process, researchers strategically place water-filled glass test tubes plugged with cotton within the drying soils. The gradual loss of moisture prompts the fire ants to migrate from the drying soil to the moist cotton, resulting in successful extraction without the usual high mortality.
F.M. Shah and colleagues observed, "Once the soil dried out, IFA moved from trays to moist cotton in the test tubes to avoid dehydration." This method allows not only for the effective capture of worker ants but also ensures the full recovery of queens and various life stages of ants, leading to the successful establishment of laboratory colonies.
Comparatively, the moisture differential technique allowed for the extraction of 52% more colony mass than the water dripping method. This is particularly important as maintaining healthy and populous colonies ensures reliable data for scientific research. Post-separation survival rates also significantly improved, showcasing the technique's effectiveness.
The research was conducted during the late fall of 2022 and early spring of 2023 with findings presented on January 31, 2025. The positive results indicate not only the superior effectiveness of the moisture differential technique but also its potential for wider application. By enabling the maintenance of healthy fire ant colonies for longer periods, researchers can engage in extensive studies without the constant need for colony replacement.
"All stages including the queens were successfully extracted using this technique," stated the researchers, emphasizing the technique's comprehensiveness. Notably, the method could also find additional applications, particularly for behavioral bioassays requiring minimal disturbance to colony dynamics.
Overall, the moisture differential technique places the study of fire ants on firm ground, paving the way for enhanced research methodologies addressing the challenges of traditional extraction techniques. This innovation is expected to advance not only the management of laboratory fire ant colonies but also the broader scientific inquiry related to this pest's ecology and control.
Future studies are anticipated to explore the long-term applications of this technique, potentially modifying elements such as moisture levels to suit various experimental needs within fire ant research. By refining techniques for maintaining these colonies, researchers can continue to unravel the complex behaviors and effects of the important agricultural pest.