A study of morphological characters of 4,000 adult weevils used in preparing a key and descriptions indicates there are fifteen North American species in the genus Tychius Germar. Adults occur on plants in the genera Astragalus, Baptisia, Hedysarum, Lotus, Lupinus, and Oxytropis.
The genus is divided into two species groups. The T. sordidus group appears to have representatives in the Old World fauna, but the T. semisquamosus group is probably native to North America. New names, Tychius caesius, and T. hirsutus are proposed for T. armatus Green, 1920 (not Tournier, 1873), and T. hirtellus LeConte, 1876 (not Tournier, 1873) respectively. Three species, T. badius, T. montanus, and T. phalarus, are described as new. A neotype is designated for T. aratus Say. Lectotypes are designated for T. Tomentosus (Herbst), 1785, T. stephensi Schoenherr, 1836, T. lineellus LeConte, 1876, T. semisquamosus LeConte, 1876, and T. hirtellus Le- Conte, 1876. The name Paratychus Casey, 1910, is newly placed in synonymy with Tychius Germar, 1813.
Clark, Wayne E.
"A taxonomic revision of the weevil genus Tychius Germar in America north of Mexico (Coleoptera: Curculionidae),"
Brigham Young University Science Bulletin, Biological Series: Vol. 13
, Article 1.
Available at: http://scholarsarchive.byu.edu/byuscib/vol13/iss3/1