Quest 1948 Pipistrellus hesperus 7 June 30 San Luciano, 100+ feet, 5 mi S. Santa Rosalia, Baja California that this species ranged over a larger amount of terrain than the Eptesicus fuscus which confines their range to the limits of the cornfield. Dr. Benen netted one that was flying low over what looked like large Encelia bushes near the pond. Saw two of this species chasing each other in close curves and spirals for at least 10 seconds. They were seen over the rock fence bordering the cornfield. July 12 Catawiña, 1350+ ft. Baja California One male and three females obtained this evening before and after sundown. All were shot as they flew up and down the wash west of the ranch. Two of this species were seen flying together down the wash before sundown, their being illuminated by the light of the setting sun. They were definitely associated with each other, one continuously flying up to and darting around the other. After sun- down they became much more common and about fifteen were seen feeding about a small mosquito in the wash.