Rhyssomatus

Species occupy diverse habitats including agricultural fields, prairie remnants, and disturbed areas. R. nigerrimus and R. subtilis are strongly associated with soybean cultivation regions. R. lineaticollis inhabits fragmented prairie landscapes with Asclepias syriaca patches. Some species utilize weedy alternate host plants when primary hosts are unavailable.

Widespread in the Americas. R. nigerrimus occurs in Mexico. R. subtilis is endemic to northwestern and northeastern Argentina, with recent range expansion to Córdoba Province. R. lineaticollis is found in east-central Iowa, USA. The genus as a whole ranges from North America through Central and South America based on GBIF records including Vermont, USA.

Larval feeding occurs within plant tissues, particularly seeds and pods. Adults feed on foliage, with some species clipping leaf petioles. Several species are specialist feeders on legumes: R. nigerrimus reproduces exclusively on soybean (Glycine max); R. lineaticollis is monophagous on Asclepias syriaca; R. subtilis is oligophagous on soybean and dry beans. Some species utilize alternate host plants for adult feeding and refuge when primary hosts are unavailable.

• Glycine max - PRIMARY_HOST_REPRODUCTIVEsoybean; exclusive reproductive host for R. nigerrimus and R. subtilis
• Asclepias syriaca - PRIMARY_HOST_REPRODUCTIVEcommon milkweed; exclusive host for R. lineaticollis
• Sesbania punicea - PRIMARY_HOST_REPRODUCTIVEreproductive host for R. marginatus in South Africa biological control context
• Rottboellia cochinchinensis - ALTERNATE_HOSTalternate host for R. nigerrimus adults during rainy season
• Hyparrhenia rufa - ALTERNATE_HOSTalternate host for R. nigerrimus adults
• Sorghum halepense - ALTERNATE_HOSTalternate host for R. nigerrimus adults; strongest EAG response
• Ipomoea trifida - ALTERNATE_HOSTalternate host for R. nigerrimus adults
• Crotalaria pallida - ALTERNATE_HOSTtested in olfactometer studies with R. nigerrimus
• Crotalaria retusa - ALTERNATE_HOSTtested in olfactometer studies with R. nigerrimus
• Crotalaria spectabilis - ALTERNATE_HOSTtested in olfactometer studies with R. nigerrimus
• Crotalaria verrucosa - ALTERNATE_HOSTtested in olfactometer studies with R. nigerrimus
• Phaseolus vulgaris - ALTERNATE_HOSTcommon bean; tested in olfactometer studies
• Vigna unguiculata - ALTERNATE_HOSTcowpea; tested in olfactometer studies

Most studied species are univoltine. R. nigerrimus overwinters as pupae in soil, emerging after spring rains. Adults initially colonize weedy alternate host plants for floral resources, then move to soybean where mating occurs on pods. R. subtilis larvae develop within pods feeding on seeds, then exit and drop to soil to pupate. R. lineaticollis exhibits similar soil-dwelling pupal stage. Generation time appears synchronized with host plant phenology, particularly pod development stages.

Several species form mating aggregations on host plants. R. nigerrimus adults congregate in dense clusters on soybean leaves and pods, with mating most frequently observed midday. Acoustic communication has been documented: R. nigerrimus produces low-volume stridulatory sounds via elytra-abdomen rubbing, with two distinct patterns (paired chirps and series of chirps) that vary with group size and sex. Paired chirps may function in species recognition; series of chirps associated with stress or disturbance. R. lineaticollis is sedentary with limited dispersal (50% of recaptures move <1 m, maximum <1 km). Females of some species exhibit meticulous oviposition site selection to minimize intraspecific larval competition.

Significant agricultural pests requiring insecticide management. R. subtilis, R. nigerrimus, and related species cause direct yield loss through larval seed feeding and pod damage. Some species serve as biological control agents: R. marginatus was introduced to South Africa for control of invasive Sesbania punicea, where it supplements primary agent Trichapion lativentre by destroying up to 88% of remaining seeds. The genus represents a model for studying herbivore-plant interactions, acoustic communication in weevils, and movement ecology in fragmented landscapes.

Major economic impact on soybean production in Mexico and Argentina. R. nigerrimus and R. subtilis are managed with insecticide seed treatments and foliar applications. Research toward reduced-risk management includes development of acoustic traps for monitoring, identification of host plant volatiles for lure-based trapping, and use of alternate host plants as attractants. R. marginatus demonstrates potential for classical biological control of invasive legumes. The genus has been subject to extensive research on resistance monitoring for transgenic crop target pests.

• Sternechus subsignatusco-occurs with R. subtilis on soybean in Argentina; distinguished by larger size and stem-boring habit versus pod-feeding in Rhyssomatus
• Promecops carinicollisco-occurs with R. subtilis on soybean in Argentina; distinguished by smaller size and leaf-feeding habit versus pod-feeding in Rhyssomatus
• Trichapion lativentreco-occurs with R. marginatus on Sesbania punicea; distinguished as apionid weevil with flower-bud feeding versus seed-feeding in Rhyssomatus

• agricultural pest
• soybean pest
• acoustic communication
• stridulation
• biological control
• legume specialist
• univoltine
• pod borer
• seed feeder
• Curculionidae
• Coleoptera
• Mexico
• Argentina
• USA
• movement ecology
• host plant volatiles
• integrated pest management

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Rhyssomatus nigerrimus - Entomology Today
• “Picudo negro” (black weevil) on soybean in Argentina | Beetles In The Bush
• Eavesdropping on Soybean Weevils: Scientists Detect Subtle Acoustic Signals
• May | 2014 | Beetles In The Bush
• Curculionidae | Beetles In The Bush
• Argentina | Beetles In The Bush
• New Host Plants for Soybean Weevil, Rhyssomatus nigerrimus1, in Mexico
• Acoustic behavior of the adult soybean weevil, Rhyssomatus nigerrimus (Coleoptera: Curculionidae)
• Attraction of Rhyssomatus nigerrimus (Fahraeus) (Coleoptera: Curculionidae) to Odors from Alternate Host Plants
• Induced volatiles in the interaction between soybean (Glycine max) and the Mexican soybean weevil (Rhyssomatus nigerrimus)
• Olfactory responses of the soybean weevil Rhyssomatus nigerrimus to the scent of alternate host inflorescences
• Subterranean Distribution and Seasonal Emergence from Soil of Adults of Rhyssomatus nigerrimus 1 Fahraeus, 1837
• Oviposition patterns and the supplementary role of a seed-feeding weevil, Rhyssomatus marginatus (Coleoptera: Curculionidae), in the biological control of a perennial leguminous weed, Sesbania punicea
• Movement patterns of Rhyssomatus lineaticollis Say (Coleoptera: Curculionidae) within and among Asclepias syriaca (Asclepiadaceae) patches in a fragmented landscape
• Geographical Distribution and New Host Associations ofRhyssomatus subtilis(Coleoptera: Curculionidae) Northwestern in Argentina
• First Report of the Black Soybean Weevil Rhyssomatus subtilis Fiedler (Coleoptera: Curculionidae) in Córdoba, Argentina. Crop Damage Estimation