México (Sonora, Baja California, Baja California Sur): Three weeks (29 June–19 July, 2005), funded by the NSF REVSYS Vaejovidae grant. Grant PI Lorenzo Prendini, Ph.D. Student Edmundo González, AMNH Scientific Assistant Randy Mercurio, and REVSYS Collaborator Warren Savary returned to the Baja California peninsula, to collect vaejovid scorpions for morphological study and DNA isolation and survey more generally the arachnid fauna of this arid desert peninsula. The expedition was undertaken by two teams in separate vehicles. Prendini and Savary embarked from Oakland, California, stopping to collect scorpions in Monterey County, before meeting in Tijuana with Mercurio and González, who had returned from the Pinacaté Desert in northwestern Sonora. Both teams traveled south in convoy until reaching Guerrero Negro, near the where they split up, leap-frogging at various stations on the way down to Cabo San Lucas along the Sea of Cortez and the Pacific coast. From Cabo San Lucas, the teams turned northward and traveled a figure-of-eight along the Pacific coast and the Sea of Cortez as far as San Felipé before returning to Tijuana along the U.S. border. Despite low points (vehicle accident, breakdown, three flat tires, twice stuck in the sand), the trip, which covered more than 8,000 km from the top to the bottom of the peninsula in three weeks, yielded over 1,000 specimens, including all (14) genera and most (42) species of scorpions recorded from the peninsula, as well several solifuges, amblypygids and spiders. Highlights included a new Serradigitus and potential new Paruroctonus and Vaejovis that await further study.