Most of the limnological studies in India have focussed on a few taxa of large, permanent water bodies, and pond ecosystems, and related temporary water bodies are neglected. We present here a faunal inventory, with representative photographs, for a single, small temporary pond, reporting over 125 species of strictly aquatic fauna and 25 species of associated fauna, even though we did not identify some groups such as Protozoa, Diptera and nymphs of Odonata, etc. The identified species belong to seven taxa of vertebrates and invertebrates together. Arthropoda and Rotifera were the most species rich groups, observed with 83 and 45 representatives, respectively. Coleoptera were the most numerous in terms of species number. Such a small water body holds some endemics as well as otherwise very rare animals and so deserves better attention. We also highlight the potential and importance of such habitats for research and conservation.

Species of the genus Coelostoma Brullé, 1935 belonging to the subgenera Coelostoma s. str. and Holocoelostoma Mouchamps, 1958 from the Indian subcontinent are revised. Six species of Coelostoma s. str. and two species of Holocoelostoma are recognized, of which two are described as new: C. (Coelostoma) lyratum sp. nov. (India: Maharashtra) and C. (Coelostoma) nostocinum sp. nov. (India: Maharashtra, Goa, Karnataka, Kerala). Coelostoma (Coelostoma) fallaciosum Orchymont, 1936 and C. (Coelostoma) vividum Orchymont, 1936 were recorded for the first time from India and Bangladesh, respectively. Lectotypes are designated for C. aeneolum Régimbart, 1903 and Hydrobius stultus Walker, 1858. The previously confusing situation with Coelostoma (Holocoelostoma) stultum (Walker, 1858) and C. (Holocoelostoma) bhutanicum Jayaswal, 1972 is clarified based on new material of both species from India. Coelostoma sulcatum Pu, 1963 from China is removed from the synonymy of C. stultum and considered as a likely synonym of C. bhutanicum, a status which needs to be confirmed by a detailed study of type specimens. All species are (re)described and illustrated. Diagnosis of the subgenera of Coelostoma are modified in order to accommodate the species of the Indian subcontinent, resulting in narrowing down the concept of Coelostoma s. str. and widening the concept of Lachnocoelostoma Mouchamps, 1958.

The Copelatus species occurring in Maharashtra State, India, are reviewed. Altogether, nine species are recorded, three of which are described as new: Copelatus deccanensis sp. nov. (C. nigrolineatus species group), C. maushomi sp. nov. (C. consors group) and C. bezdeki sp. nov. (C. irinus group). Habitus and male genitalia are illustrated for all Copelatus species from Maharashtra, a key to the species and distribution maps are presented. New distributional records along with short diagnoses of already known species are provided. In addition, the study of extensive material of Copelatus species from the Indian subcontinent outside Maharashtra revealed the following new synonymies: Copelatus freudei Guignot, 1955 = C. gibsoni Vazirani, 1974 syn. nov. = C. gibsoni Vazirani, 1975 syn. nov. = C. spangleri Vazirani, 1974 syn. nov. = C. spangleri Vazirani, 1975 syn. nov.; Copelatus oblitus Sharp, 1882 = C. karnatakus Holmen & Vazirani, 1990 syn. nov.; C. sociennus J. Balfour-Browne, 1952 = C. bangalorensis Vazirani, 1970 syn. nov.; Copelatus tenebrosus Régimbart, 1880 = C. ceylonicus Vazirani, 1969 syn. nov. = C. assamensis Vazirani, 1970 syn. nov.

We studied faunistic and ecological factors influencing distributions of aquatic beetles in the Northern Western Ghats (NWG) of India. In the period 2013–2017, we collected 213 samples from 105 localities within the area and obtained 66 species, the majority of which belong to Dytiscidae. Relative occurrence based on incidence data revealed that dytiscid water beetle Laccophilus inefficiens as the most widespread species. Non-parametric richness estimators Chao2, Jackknife1 and Bootstrap showed that 70–80% of the fauna was covered in the sampling efforts from different types of freshwater habitats. Sample-based rarefaction suggested that more sampling efforts within the region can yield additional species. Canonical correspondence analysis (CCA) revealed that altitude, salinity, hydroperiod and depth influenced the distribution of aquatic beetles. Further, CCA also revealed habitat preference and co-occurrence of various aquatic beetle species. For instance, while co-occurring species under Laccophilinae and Hydroporinae were eurytopic, other co-occurring species Clypeodytes hemani, Microdytes sabitae and Lacconectus lambai were restricted to temporary habitats. Multiple correspondence analysis (MCA) showed a strong association between altitudinal classes and species distribution where many species were restricted within a particular altitudinal gradient. For example, M. sabitae, C. hemani, Hygrotus nilghiricus, L. lambai and Rhantus taprobanicus with classes 900–1199 and 1200–1499 while Hyphydrus flavicans, Laccophilus ceylonicus, Lacconectus andrewesi, Sternolophus inconspicuus and Canthydrus laetabilis with the class 300–599. The present work on aquatic beetles is the first attempt to study the influence of environmental factors on species diversity and distribution in the Northern Western Ghats of India.

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