Notes on the Anisoptera fauna near Mazatlan, Mexico, including dry to wet seasonal changes

Anisoptera were studied near Mazatlan, Sinaloa, Mexico during the period 22 June to 24 July 1975. The summer rains began on 5 July. The relative abundance of 19 species before and after 5 July was noted, with 6 species present in the dry season and increasing in numbers in the wet season, 5 species present and increasing only in the wet season, 4 species remaining at the same population level, and 3 species present in the dry season but decreasing as the wet season progressed. Erythrodiplax funerea (Hag.) was present in the forest in the dry season, rapidly gathered at newly formed temporary pools for a few days, then decreased in abundance. Twenty-six species of anisoptera were collected in the vicinity of Mazatlan. Data on behaviour, coloration, and egg hatching times that seem especially noteworthy are given. The known range of Libellula gaigei Gloyd is extended 990 km to the northwest.