Developing marking techniques to study movement and foraging of Argentine ants (Hymenoptera: formicidae)

Fat and water soluble dyes were tested to determine if they were suitable as markers for Argentine ant, Linepithema humile (Mayr), for field studies. Sudan black was visible in ants, but caused significant mortality of workers. The water soluble dye Calcofluor M2R (CW) and Fluorescent Brightener 28 (FB 28) were readily consumed in sugar water solutions and did not kill workers. As little as 0.01 ng samples of CW or FB 28 were visible under long-wave ultraviolet light. The ants retained the CW and FB 28 for at least 8 weeks. The highest level of fluorescing was detected in the abdomen of workers. The CW and FB 28 provided a stable marker that could be fed to workers In sugar water and detected at extremely low levels.