Figure 19 from: Bousquet Y (2012) Catalogue of Geadephaga (Coleoptera: Adephaga) of America, north of Mexico. ZooKeys 245: 1-1722. https://doi.org/10.3897/zookeys.245.3416

Figure 19 - Promecognathus crassus LeConte. This species, along with its close relative Promecognathus laevissimus, are western coastal elements that feed on polydesmid millipedes. The adults straddle their prey, moving quickly toward the head to pierce the neck and sever the ventral nerve cord with their long mandibles, thereby preventing the millipedes from using their cyanide defense spray. Promecognathines represent a very old, relic lineage, likely originating from Pangea, represented today only in western North America and the Cape Province in South Africa.