Broad geographic regions in which the species have been observed, based on published records, are indicated by two-letter codes in brackets following the valid species names. These codes and their areas are indicated on the accompanying map of North America:
- FN=far north (above the 60th parallel)
- FS=far south (below the Tropic of Cancer)
See Species List for usage examples. In addition actual countries of distribution are also given:
- USA=United States
As an example, USA:FN indicates an Alaskan distribution whereas MEX:SW indicates a northern Mexican distribution. Only FS and SE are unique to one country (FS to Mexico, SE to the United States).