Subterranean Distribution and Seasonal Emergence from Soil of Adults of Rhyssomatus nigerrimus1 Fahraeus, 1837

Rhyssomatus nigerrimus Fahraeus, 1837 (Curculionidae: Molytinae: Cleogonini) causes economic loss in soybeans (Glycine max L. Merr.) in Mexico. Because of this, it is convenient to know where it survives without a host and essential to know when it arrives in the crop. This work documented the distribution of larvae, pupae, and adults in the soil. It also documented the emergence period of adults in the soybean-producing area of Tamaulipas, Mexico. Larvae, pupae, and adults were sampled at 10, 20, and 30 cm from the soil surface in three soybean farms. Adults also were recorded when they emerged from the ground in 2 x 2 x 1 m emergence traps at the sites. Larvae, pupae, and adults of R. nigerrimus were at 10, 20, and 30 cm from the soil surface. Many pupae and adults were recorded at 10 cm. In the soil, pupae were found from February to May, larvae from January to March, and adults from March to November. Adults emerged from the soil from June to November. Based on results, the weevil R. nigerrimus has a single generation per year and two development phases: an active one that occurs in the soybean crop, and a dormant phase in the soil.