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

The soybean weevil, Rhyssomatus nigerrimus (Fahraeus) (Coleoptera: Curculionidae) is an economically damaging pest on soybean in Mexico. Adult weevils are managed with insecticides. Reduced risk management could include the development of traps for monitoring. Adult weevils form mating aggregations on soybean and produce low-volume sounds. The objective was to characterize the sounds produced by groups of males and females, and to determine whether the weevil group size influences the acoustic signals. Adult weevils were field collected and then sorted into groups of males and females in the laboratory. Groups of adult males or females (3, 5, or 10) were used for acoustic recordings. Adobe Audition software was used to visualize and measure the duration and peak fundamental frequency of the sounds. Two acoustic signal patterns were produced by both males and females: paired chirps and a series of chirps. Paired chirps were produced by all group sizes of males and females. The series of chirps was produced by larger groups of males more frequently than smaller groups. For females, the series of chirps was detected more frequently in small groups of 3 females than in larger groups. Paired chirps may play a role in species identification; they have been characterized for other weevil species, and chirp durations vary among the species recorded. The series of chirps produced occur in other weevil species as well and are associated with stress or disturbance. The acoustic patterns produced by R. nigerrimus and their behavioral context could be further explored for potential inclusion in an acoustic trap to detect and monitor this weevil.