Electrically stimulated fire ants (Solenopsis invicta, Hymenoptera: Formicidae) release chemical cues that attract parasitic pseudacteon decapitating flies (Diptera: Phoridae)

Authors: Vander Meer, Robert; PORTER, SANFORD - Retired ARS Employee; CARDOZA, YASMIN - Retired Non ARS Employee

Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/7/2026
Publication Date: 5/13/2026
Citation: Vander Meer, R.K., Porter, S.D., Cardoza, Y.J. 2026. Electrically Stimulated Fire Ants (Solenopsis invicta, Hymenoptera: Formicidae) Release Chemical Cues That Attract Parasitic Pseudacteon Decapitating Flies (Diptera: Phoridae). Journal of Chemical Ecology. 52:44. https://doi.org/10.1007/s10886-026-01710-w.
DOI: https://doi.org/10.1007/s10886-026-01710-w

Interpretive Summary: Phorid flies, parasites of fire ants, are able to find their host Phorid flies, parasites of fire ants, are able to find their host fire ants. We used phorid fly mass rearing containers as bioassay arenas to evaluate the effect of various fire ant glandular extracts on activating attacking phorid flies. The Dufour's gland, source of the recruitment pheromone had no affect on the parasitic flies. Poison sac extracts showed low level fly attraction; however, the purified venom alkaloids, derived from the extracts had no effect on the phorid fly parasites. Interestingly, shaken ants release the fire ant alarm pheromone, and significantly activated phorid flies. However, the attraction dissipated quickly. Synthetic alarm pheromone dissolved in mineral oil was immediately highly attractive to the flies and that attraction lasted several minutes. We demonstrate that the fire ant alarm pheromone is responsible for phorid fly attraction to fire ants. This research may benefit the large scale rearing of phorid flies as biocontrol agents of imported fire ants.

Technical Abstract: We previously determined that electrically stimulated fire ants release exocrine gland products, e.g., venom, recruitment and alarm pheromones. We hypothesized that exocrine gland emissions from electrically stimulated fire ant workers might attract phorid fly parasitoids of fire ants. Bioassays demonstrated that electrically stimulated worker ants did attract phorid fly parasitoids in the field. Phorid fly (Pseudacteon tricuspis) mass rearing boxes were then used for lab bioassays to determine the glandular source and active components from electrically stimulated fire ants that elicited phorid fly attraction. Neither fire ant venom nor purified venom alkaloids affected phorid flies. Likewise, Dufour’s glands (the source of recruitment pheromones) elicited no fly activation/attraction. However, mandibular glands extracts, the source of alarm pheromones were found to activate and attract phorid flies. Moreover, a previously identified pyrazine alarm pheromone from mandibular glands was found to be the active component. This was confirmed by specific alarm pheromone bioassays showing the expected ephemeral characteristic of the attraction and by directly using synthetic fire ant alarm pheromone. Use of the fire ant alarm pheromone may aid in detecting the presence of phorid flies in the field and in increasing attack/parasitism rates during mass production.