Date of this Version
Selected taxonomic characters of Apion species are redefined and explained including subcephalic ridge, sensory seta and macrochaeta. New species described are Apion (Trichapion) memnonmonum Kissinger, Black Mountains, North Carolina and Apion (Trichapion) nelsoni Kissinger from Davis Mts, Texas and Santa Rita Mts, Arizona. Supplemental descriptions or new records are given for the following species: Apion aequabile Fall, A. brunnicornis Fall, A. eccentricum Fall, A. minor Smith, A. punctulirostre Sharp and A. submetallicum Boheman.
A statistical test is used to evaluate the importance of a character in defining species groups in the Apion subgenus Trichapion Wagner. Eighteen characters met this criterion and were used to define 12 species groups. A method is presented to evaluate membership in a species group. The inclusion probabilities for a list of 82 species is given for each of 12 species groups of Trichapion occurring in North and Central America.