A new subgenus of Bembidion, Geocosmius subg. nov., is described from forests of México and Guatemala.  Geocosmius includes Bembidion nahuala Erwin as its type species, as well as B. franiaeErwin, B. elescarabajo sp. nov., and additional forms similar to B. nahuala. In México this subgenus is widespread, ranging from Chiapas and Oaxaca north and west to Jalisco, Querétaro, and Hidalgo; most specimens are from cloud forests between 1700–2700m in elevation.  A molecular phylogenetic analysis based upon eight genes indicates that Geocosmius is the sister group of subgenus Liocosmius, from western North America.  In addition, a new species of subgenus Liocosmius, B. cachagua sp. nov., is described from three localities in California.  Illumina sequencing was used to acquire DNA sequences of six pinned, dried specimens, which ranged in age from 24 to 57 years, allowing the phylogenetic placement of four of the studied species to be determined.

For one sample, extracted DNA was subjected to PCR, and the products Sanger sequenced.  For most samples, however, DNA was sequenced on an Illumina HiSeq (various models), and the resulting paired reads were trimmed and assembled using CLC Genomics Workbench.  Target genes were then acquired from those assemblies using BLAST. Maximum likelihood analysis was conducted using IQ-TREE.