Two groups of Tenthredo associated with the verticalis lineage are reviewed. The species of both groups are found east of the Rocky Mountains with a centre of diversity along the Appalachian range. All species are native to North America.
Thirteen new species are described, all belonging to the verticalis group: Tenthredo applachicola, T. bilucens, T. binotata, T. cingulatoides, T. elongata, T. fawnae, T. flaviocciput, T. gibsoni, T. lucifer, T. micheleae, T. nigritarsalis, T. paraverticalis, and T. rufiscutum. Four new synonyms are proposed: Tenthredo glacialis Ross, 1931, syn. nov. of T. carolina (Rohwer, 1913); T. borealis Kirby, 1882 (a primary homonym), syn. nov. of T. bella (T. nordica Goulet nom. nov. for T. bella Cresson, 1880, a primary homonym); T. angulata Norton, 1864, syn. nov. of T. lobata (Norton, 1860); T. nortoni Smulyan, 1915, syn. nov. of T. lobata (Norton, 1860), and T. pallicola MacGillivray, 1895, syn. nov. of T. eximia Norton, 1868. Three previously synonymized species are re-instated: Tenthredo cingulata Provancher, 1878 [a primary homonym renamed here as Tenthredo leoni Goulet, nom. nov.], T. nova MacGillivray, 1897 (incorrectly synonymized under T. eximia which belong to another species group), and T. rubripes MacGillivray, 1900 [a primary homonym renamed here as T. transversolinea Goulet, nom. nov.]. Tenthredo mantha Ross, 1951, a replacement name for Tenthredella lobata maculosa Smulyan, 1915, was considered to be unnecessary and Tenthredo maculosa (Smulyan) is re-instated.
Lectotypes are designated for Allantus angulifer Norton, 1860, A. mellinus Norton, 1860, Tenthredo formosus Norton, 1864, T. eximius Norton, 1868, T. borealis W. F. Kirby, 1882, T. bilineatus MacGillivray, 1895, T. novus MacGillivray, 1897, T. simulatus MacGillivray, 1897, T. rubripes MacGillivray, 1900, T. causatus MacGillivray, 1900, and T. rutata MacGillivray, 1923. A neotype is designated for Tenthredo verticalis Say, 1824.
Keys to lineages of Nearctic Tenthredo and to some groups within the verticalis lineage are provided to help the user in recognizing the species groups reviewed here.
All species of the two groups are keyed. Each group of species is characterized and taxonomic notes are provided. For each species, the following (if available and/or pertinent) is included: synonymic list, diagnosis, description of the known sexes, geographical variation, taxonomic notes, derivation of the specific epithet, biological notes, phenology and distribution range.