ExclusiveThe Common Buckeye Image of the Month TrueToad - September 10, 2016 A common buckeye caterpillar shown on a host plant. This species is resident across the southern United States, much of Mexico and as far north as southern Canada. When in the butterfly state, it regularly expands its range each year northward to temporarily colonize much of the U.S., reaching Canada. Starting in late summer and continuing through fall, huge numbers of adults migrate southward, where the adults overwinter.