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. 2019 Dec 13;10(12):451.
doi: 10.3390/insects10120451.

Electrophysiological and Alarm Responses of Solenopsis invicta Buren (Hymenoptera: Formicidae) to 2-Ethyl-3,5-dimethylpyrazine (Short Title: EAG and Behavioral Responses of Fire Ants to Pyrazine)

Ya-Ya Li  1   2   3 , Deguang Liu  1   3 , Li Chen  2
Affiliations

Electrophysiological and Alarm Responses of Solenopsis invicta Buren (Hymenoptera: Formicidae) to 2-Ethyl-3,5-dimethylpyrazine (Short Title: EAG and Behavioral Responses of Fire Ants to Pyrazine)

Ya-Ya Li et al. Insects. .

Abstract

2-Ethyl-3,5-dimethylpyrazine is an isomer of 2-ethyl-3,6-dimethylpyrazine, the alarm pheromone component of the red imported fire ant, Solenopsis invicta Buren. The pyrazine was synthesized and its alarm activity was investigated under laboratory conditions. It elicited significant electroantennogram (EAG) activities, and released characteristic alarm behaviors in fire ant workers. The EAG and alarm responses were both dose-dependent. Two doses of the pyrazine, 1 and 100 ng, were further subjected to bait discovery bioassays. Fire ant workers excited by the pyrazine were attracted to food baits, and their numbers increased over time. Ants displayed very similar response patterns to both low and high doses of the pyrazine. The pyrazine impregnated onto filter paper disc attracted significantly more fire ant workers than the hexane control for all observation time intervals at the low dose, and in the first 15 min period at the high dose. The pyrazine loaded onto food bait directly tended to attract more fire ant workers than the hexane control. These results support the potential use of 2-ethyl-3,5-dimethylpyrazine to enhance bait attractiveness for the control of S. invicta in invaded regions.

Keywords: alarm pheromone; antennal response; bioassay; myrmecology; red imported fire ant; social behavior.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Chemical structures of pyrazines.
Figure 2
Figure 2
An electroantennogram (EAG) dose–response curve for Solenopsis invicta workers responding to 2-ethyl-3,5-dimethylpyrazine (mean ± SE, n = 8). The doses shown are the chemical mass that was impregnated on filter paper strips, not the actual doses delivered to the antennal preparation.
Figure 3
Figure 3
Alarm dose–response curve for Solenopsis invicta workers responding to 2-ethyl-3,5-dimethylpyrazine (mean ± SE, n = 10). The doses shown are the chemical mass that was impregnated on filter paper strips.
Figure 4
Figure 4
Attractiveness of 2-ethyl-3,5-dimethylpyrazine-treated hotdog baits to Solenopsis invicta workers. (A) 1 ng; (B) 100 ng. Means within the same time period with different letters are significantly different at p < 0.05, ANOVA followed by the Tukey-HSD test, and no letters indicate no differences between treatments.
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