Tachysphex pechumani, the antenna-waving wasp, has a disjunct geographic distribution in the Lower Peninsula of Michigan, Indiana Dunes, Oak Openings of Ohio, southern Ontario, and New Jersey pinelands. This distribution is tied to excessively/well-drained sandy soils, oak/pine-dominant barrens, savanna and woodland, climate moderation related to proximity to large bodies of water, habitat fragmentation from natural causes and human disturbance, and 20^th-century land preservation. The 550-km gap between subpopulations in southwestern Ontario and southern New Jersey may be the consequence of Early Holocene pine-dominant barrens, savanna, and woodland being supplanted by deciduous and deciduous-coniferous forest on loamy sand in the northeastern United States during the past 6000 years. A plausible scenario as to where T. pechumani lived during the past 18,000 years and what dispersal route(s) enabled it to attain its current geographic distribution is presented.