Odonata records from Nayarit and Sinaloa, Mexico, with comments on natural history and biogeography

Although the odon. fauna of the Mexican state of Nayarit has been considered well-known, a 7-day visit there in Sept. 2001 resulted in records of 21 spp. new for the state, bringing the state total to 120 spp., fifth highest in Mexico, Records from a 2-day visit in Aug. 1965 are also listed, many of them the first specific localities published for Nayarit, and the first records of 2 spp. from Sinaloa are also listed. The biology of most neotropical spp. is poorly known, so natural-history notes are included for many spp, A storm-induced aggregation and a large roost of dragonflies is described. The odon. fauna of Nayarit consists of 2 primary elements: a large number of neotropical spp. reaching their northern known limits, and a montane fauna of the drier Mexican Plateau. At least 57 spp. of tropical origin reach their northern distribution in the western Mexican lowlands in or N of Nayarit, and these limits must be more accurately defined to detect the changes in distribution that may be taking place with global climate change.