The Geographic Distributions of Cicada Killers (Sphecius; Hymenoptera, Crabronidae) in the Americas

The distributions of American cicada killers (Sphecius) were examined via solicited and museum specimens. S. hogardii occurs in southern Florida and several Caribbean islands. S. speciosus occurs throughout the east coast, southeast, and Midwestern states at high densities, and its range extends much farther west than expected, but not west of the continental divide. S. speciosus appears to be excluded from high altitudes. S. grandis and S. convallis occur at higher altitudes and are largely sympatric throughout the west, but are most common in lower riparian regions. Sphecius grandis is found at significantly higher altitudes than S. convallis. Both are sympatric with S. speciosus on both sides of the Rio Grande. The northern boundaries of Sphecius extend to 48.2oN latitude, and are associated with well known faunal zones. The continental divide may have served as a geographic barrier, playing a role in the evolution of American Sphecius by allopatric speciation.