|Vander Meer, Robert - Bob|
Submitted to: Journal of Insect Behavior
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/7/1997
Publication Date: N/A
Citation: Interpretive Summary: Reproduction in the red imported fire ant, Solenopsis invicta Buren, begins with synchronized mating flights during which male and female winged reproductives, called alates, leave their natal nests and mate several hundred meters in the air. Just prior to a mating flight, worker fire ants open up holes in the nest surface and swarm excitedly on top of the nest. The purpose of this heightened worker activity may be to protect and aid the alates as they prepare to fly. Previous studies indicate that the male and female alates produce a chemical substance that elicits excitement in the worker ants. We investigated the glandular source of chemicals in fire ant alates that cause such excited reactions in the workers. We first tested crushed heads, thoraces, and abdomens of both male and female alates and found that only the head consistently caused an excited reaction in worker ants. Some reaction was caused by crushed female alate abdomens, but this was likely due to the presence of a chemical that attracts the workers to the female, rather than causing excitement. We then dissected mandibular, post-pharyngeal, and poison glands from the alates and found that only mandibular glands (attached to the mandibles or jaws) of both male and female alates caused excitement. Our next study will identify the chemicals involved. The rapid searching movement caused by these chemicals may be useful in making fire ant baits more effective.
Technical Abstract: At the onset of mating flights in Solenopsis invicta, workers swarm excitedly over the mound as alates prepare to fly. Previous studies demonstrated that this excitement is stimulated by the male and female alates. We investigated the glandular source(s) of pheromones produced by the alates that cause excitement. The only common female and male alate body part that elicited excitement when crushed was the head. Within the head, excised mandibular glands were found to be responsible for worker excitement. Fire ant workers are very sensitive to external stimuli and some excitement was elicited by crushed female gasters and male thoraces, but the response was never as significant as crushed heads. Tests with summer and winter alates revealed similar results, except that gasters of winter female alates had a greater excitant effect than did gasters of summer female alates. This may be due to the production of attractant pheromones by the poison glands of overwintering female alates. We conclude that the mandibular gland is the source of alate excitant pheromones.