The paper describes and maps stripe pattern variability in the damselfly Argia apicalis (Say) along the periphery of its southeastern distribution. Two major variations exist. One, the broad-striped form, has a wide, full-length humeral stripe and, in females, a well-developed middorsal thoracic stripe. Broad-striped specimens also possess larger areas of black pattern on the dorsum of the head and, in males, on the eighth and ninth abdominal segments. The second, typical form, has a reduced pattern characterizing populations west and north of southeast Georgia and northern Florida. The southeastern margin of distribution consists of broad-striped populations representing four groups of isolated populations. Isolation results from low interchange between colonies of different river systems and, within the southeast, lack of colonies on lakes, ponds, smaller streams, and river headwaters. One intergradation area between typical and broad-striped populations is known. A discussion follows relating origin of the variability to Pleistocene habitat changes.