Quest 1948 Pipistrellus hesperus 3 May 17 Trunfo, 1700 ft. Baja California One male and one female (2 Emb., 8mm) shot at sunset yesterday evening. The species was at its greatest concentration over the wash at sunset, decreasing in numbers seen until half an hour later when none were seen. The bats were feeding around Mesquite trees and up and down the wash below our camp. The Pipistrellus started feeding about 15 minutes before larger species were seen in the air. Tonight the Pipistrellus appeared at 6:30, feeding around the mesquite trees. The larger bats appeared at 7:00 P.M. It was quite cloudy in the west this evening possibly causing an early appearance of the bats. Two females were shot (#197,198) containing each 2 embryos of 7 and 8mm respectively. May 18 Same Location. The species did not appear until 7 P.M. this evening possibly because of the complete absence of clouds or overcast at sunset. Dr. Benson shot one. The Pipistrellus appeared at the same time tonight as Dasycyptus ega and E. pleuriscis fuscus, both of which were obtained. May 25 El Carrigalito, 1400 ft. 3 mi N San Diego, Baja California One caught last night as it flew into wire strung across water tanks at dark. Specimen (# 253) had two embryos of 10mm each.