How male fire ants ensure that the sperm passed on to a female sexual will not be displaced by other males

Fire ant mating flights occur when weather conditions are favorable (moisture, temperature, wind). Males fly first and form a lek about 150m in the air. Females sexuals then fly into the lek and mate. Males outnumber the females and it is reasonable that other males will attempt to mate with an already mated female, potentially displacing or diluting the first males sperm. However, it is reported that newly mated queens mate only once. We investigated the possible mechanism by which secondary mating is prohibited. We determined that males produce tyramides in their aedeagal bladder and transfer these compounds to the females during mating. While the majority of these compounds wind up in the female reproductive system, we found measurable amounts on the outer surface of the newly mated queen's gaster. Using a modified olfactometer, we determined that tyramides do not repell males through space; however, males would turn around and go in the opposite direction if they came in close proximity to or touched the tyramides. We propose that this is at least part of a mechanism evolved to prevent multiple mating during population-wide mating flights.