Species composition, distribution insights and seasonal variation of Odonata in the Madhuranthagam Block of Chengalpattu district, Tamil Nadu, India

Aim: To assess species composition, diversity, seasonal variation, and habitat preference of Odonata in the Madhuranthagam Block of Chengalpattu district, Tamil Nadu, India. The study also examined the influence of seasonal changes, if any, on the abundance and community structure of odonates. Methodology: Field surveys were conducted from September to December 2025 across wetlands, paddy fields, and associated habitats using fixed-area transect and visual encounter methods. Species were identified using standard taxonomic keys, and the species abundance data were analyzed using diversity indices such as Shannon-Wiener, Simpson’s, Margalef’s richness, Pielou’s evenness and Berger-Parker dominance indices. Results: A total of 1,343 individuals representing 16 species across three families were recorded in the study area, with Libellulidae being the dominant family (56%), followed by Coenagrionidae (38%) and Aeshnidae (6%). Species belonging to the suborder, Anisoptera contributed 63 per cent and Zygoptera accounted 37 per cent. Species such as Pantala flavescens, Diplacodes trivialis and Ischnura rubilio were found dominant throughout the study period. Higher abundance and diversity were recorded during September–October 2025 compared to November–December 2025, although species richness remained constant. Interpretation: The findings revealed that the monsoon-driven wetland conditions significantly enhanced the Odonata abundance and evenness, while seasonal decline affected relative abundance rather species composition. Wetlands and paddy ecosystems play a critical role in sustaining odonate assemblages in the region. The study provides a baseline data for Chengalpattu district and highlights the need for wetland conservation and habitat restoration to maintain biodiversity and ecological stability. Key words: Diversity indices, Dragonfly, Odonata, Seasonal variation, Species distribution