_Progne subis subis_ (Linnaeus): Purple Martin.--A large migrant flock of several thousand individuals of this species was present for several days in August at Rancho San Miguel. Specimens (3): [Female], 40723, ovary inactive, 48.6 gm. (August 14), [Female], 40724, 51.8 gm. (August 17), and [Female], 40725, imm. skull, 52.1 gm. (August 17), 4 km. NNE Felipe Carrillo Puerto. _Petrochelidon fulva citata_ Van Tyne: Cave Swallow.--Throughout our stay at Pisté, large numbers of Cave Swallows were seen flying in and out of the small opening of a well-like _cenote_ in the center of the village. Specimens were easily collected in a mist net placed across the opening. No young Cave Swallows were taken and gonads of adults were in various stages of reproductive activity. A few individuals taken were beginning to molt. Probably the swallows were nesting in the _cenote_ although the nests were inaccessible to view. Previous breeding records are for April (Paynter, 1955a:209). Twenty-two specimens were collected, of which the following were taken at Pisté, July 21-25: [Male], 40693, testis 6 × 3 mm., 18.4 gm.; [Male], 40696, 16.4 gm.; [Female], 40697, 18.2 gm.; [Male], 40695, 15.0 gm.; [Female], 40690, ovary inactive, 18.4 gm., molting--2nd primaries ensheathed; [Male], 40692, testis 5 × 3 mm., 17.9 gm.; [Female], 40698, 18.3 gm.; [Female], 40702, ovary 7 × 3 mm., 18.9 gm.; [Female], 40703, ovary 6 × 3 mm., 17.5 gm.; [Male], 40713, testis 3 mm., 18.4 gm.; [Female], 40704, 16.5 gm.; [Male], 40705, 20.3 gm.; [Male], 40699, testis 2 mm., 18.6 gm., molting--2nd primaries ensheathed; [Female], 40700, ovary 5 × 3 mm., 18.5 gm., molting--1st primaries ensheathed; [Female], 40701, ovary 5 × 3 mm., 16.5 gm., molting--1st primaries ensheathed; [Male], 40707, testis 7 × 5 mm., 19.9; [Male], 40708, testis 4 × 3 mm., 18.4 gm.; [Female], 40709, ovary 4 × 3 mm., 18.0 gm.; sex? 40711, 18.3 gm., molting--1st and 2nd primaries ensheathed. Additional specimens are: [Female], 40718, 16.5 gm., molting--3rd primaries ensheathed (August 16), and [Female], 40719, 18.5 gm., molting 1st primaries ensheathed (August 16), 4 km. NNE Felipe Carrillo Puerto; [Male], 40689, testis 1 mm., 16.2 gm., molting--2nd primaries ensheathed (August 10), 13 km. WSW Sisal. Mallophaga: _Philopterus excisus_, July 21; _Myrsidea_ sp. July 21 and 25.