Stenonema integrum (McDunnough) is shown to be a junior synonym of S. mexicanum (Ulmer.) n.syn. Subspecific status is delegated to Nearctic and Neotropical populations of this species as S. m. imegrum and S, m. mexicanum, respectively. Newly studied materials from Costa Rica and Belize indicate that adults of the two subspecies may be differentiated by the presence of thoracie pleural stripes in S. m. mexicanum. Consistent differentiating lanai characteristics are not known, A Pleistocene dispersal into Middle America and subsequent vicariance is hypothesized.
McCafferty, W. P.
"The Relationship Between North and Middle American Stenonema (Ephemeroptera: Heptageniidae),"
The Great Lakes Entomologist, vol 17
Available at: https://scholar.valpo.edu/tgle/vol17/iss3/2