Electrophysiological and alarm behavioral responses of Solenopsis invicta Buren (Hymenoptera: Formicidae) to alkoxypyrazines

The red imported fire ant, Solenopsis invicta produces an alarm pheromone component, 2-ethyl-3,6-dimethylpyrazine, and responds to its pyrazine analogs in a similar manner but at varied detection thresholds. Herein, the responses of fire ant workers by electroantennogram (EAG) and behavior were tested with twelve structurally-related oxygen-containing pyrazines (alkoxypyrazines) and the synthetic alarm pheromone. All tested compounds elicited a dose-dependent EAG response, with S. invicta responding greatest to the synthetic alarm pheromone. Chemical structure of pyrazines influenced the EAG response but not always alarm behavioral response. Among the 13 tested compounds, 7 compounds displayed significantly greater EAG response than 2-isopropyl-3-methoxypyrazine and 2-ethoxy-3-isopropylpyrazine at the dose of 1000 pg. Four of these 7 compounds, 2-ethyl-3,6-dimethylpyrazine, 2-methoxy-3-methylpyrazine, 2-ethoxy-3(5 or 6)-methylpyrazine, and 2-chloro-3-methoxypyrazine with characteristic substituents on pyrazine ring were further subjected to bait discovery bioassay. Hotdog bait containing pyrazines attracted significantly more fire ant workers in the first 15-min period, resulting in quicker recruitment to food block than hexane control. The potential of using alkoxypyrazines in fire ant control is discussed. (C) 2017 Published by Elsevier B.V. on behalf of Korean Society of Applied Entomology, Taiwan Entomological Society and Malaysian Plant Protection Society.