Acoustic behavior of the adult soybean weevil, Rhyssomatus nigerrimus (Coleoptera: Curculionidae)

The soybean weevil, Rhyssomatus nigerrimus (Fahraeus) (Coleoptera: Curculionidae), is an economically important pest of soybean in Mexico. This insect is generally controlled using insecticides which can have collateral effects on health, the environment and non-target organisms. Therefore, alternative monitoring and control methods such as acoustic traps are needed. The airborne sound and substrate vibration signals produced by insects play vital roles in pair formation and species recognition. The acoustic signals produced by insects can potentially be used in acoustic traps or in pheromone-baited traps to improve captures. This study investigated the acoustic signals produced by groups of male and female R. nigerrimus. Adult males and females were collected in the field during the month of October 2023, while weevils were aggregating on soybean plants. The weevils were separated by sex and kept in plastic jars with food in the laboratory. The airborne stridulations of groups of 10, 5 and 3 adults of males and females, were recorded using a microphone. The software Adobe Audition was used to visualize and measure acoustic parameters. Groups of males produced two characteristic sounds, which were pairs of chirps, or long pulse trains. Female groups similarly produced paired chirps and pulse trains. The chirp and pulse durations and frequency were measured and compared between males and females, and also among the different group sizes. The morphological structures on the abdomen associated with sound production were also investigated and are described. The results will be discussed in the context of pest management.