The aquatic bugs Anisops bouvieri Kirkaldy 1704 (Heteroptera: Notonectidae), Diplonychus (=Sphaerode-ma) rusticus Fabricius 1781, and Diplonychus annulatus Fabricius 1781 (Heteroptera: Belostomatidae) are common members of the freshwater insect communities of the East Calcutta Wetlands along the eastern fringe of Kolkata, India. These insects are established predators of dipteran larvae and other organisms. A comparative account of their predatory effi ciency was made using larvae of Culex quinquefasciatus Say 1823 in the laboratory. It was revealed that a single adult of A. bouvieri could consume 2-34 fourthinstar mosquito larvae per day, D. rusticus 11-87 fourthinstar mosquito larvae per day, and D. annulatus 33-122 fourth-instar mosquito larvae per day, depending upon the prey and predator densities. The mean predation rate of A. bouvieri and D. annulatus remained stable over a 6-day feeding period but varied for D. rusticus. The predatory impact (PI) values were 14.77-17.31, 46.9-55.73, and 61.74-72.72 larvae/day for A. bouvieri, D. rusticus, and D. annulatus, respectively. Compared to these, the clearance rate (CR) value range was 9. 06-13.25 for A. bouvieri, 13.64-15.99 for D. rusticus, and 13.50-16.52 larvae l/day/predator for D. annulatus. The values of mutual interference, "m," remained 0.06-0.78 for A. bouvieri, 0.003-0.25 for D. rusticus, and 0.09-0.27 for D. annulatus, and did not vary between the days. The difference in predatory effi ciency, CR, and PI values varied signifi cantly among the three predators, indicating the possible difference in the function as predators occupying the same guild. It can be assumed that these predators play an important role in larval population regulation of mosquitoes and thereby impart an effect on species composition and interactions in the aquatic insect communities of the wetlands and other similar habitats where they occur.

The influence of light and habitat structure on the predation of Culex quinquefasciatus larvae by the common heteropteran water bug, Diplonychus (=Sphaerodema) annulatus, D. rusticus and Anisops bouvieri was assessed in the laboratory. It was revealed that water bugs predate more in presence of light than in dark conditions. While A. bouvieri consumed more prey in structured conditions, D. annulatus and D. rusticus consumed more prey in open conditions. The selection of prey size as well as the respective numbers varied between predators and treatments significantly. Prey vulnerability (PV), an indicator of predatory efficiency, was highest for D. annulatus, moderate for D. rusticus and low for A. bouvieri. Prey consumption and PV values under different treatment conditions indicate that for belostomatid water bugs D. annulatus and D. rusticus, the order of prey consumption under different habitat and light/dark combinations is light open > dark open > light vegetated > dark vegetated. In the case of the backswimmer, A. bouvieri, the order of prey consumption appeared to be light structured > dark structured > light open > dark open. These findings were consistent with resource‐partitioning by water bug species sharing the same guild. If the observed results are extended to natural settings the efficiency of these predators in controlling mosquito populations will vary with the structural complexity of habitats and the intensity of light.

The common and abundant hemipteran water bugs Anisops bouvieri, Diplonychus rusticus, D. annulatus, of the wetlands of East Kolkata are known predators of a wide range of aquatic insects including the mosquito larvae. In the laboratory their predation were assessed in respect to short term and long term periods using the larvae of Culex quinquefasciatus to reveal their possible role in regulating the dipteran population in nature. The attack rate (a) and handling time (T h ) of these predators varied with respect to the prey size. annulatum were found to kill between 14-74 small prey and 50 -131 large prey per day, respectively. The clearance rates were found to be proportional to the predator density as well to the prey size and density, and differed between the predator species significantly. These data are supportive of qualifying the water bugs, A. bouvieri, D. rusticus, and D. annulatus as potential biological resources in regulating the population of mosquito larvae in the wetlands. IntroductionThe eastern fringe of the city of Kolkata is characterized by the perennial East Calcutta wetlands already incorporated in the list of Ramsar. Certain portions are commercially exploited for sewage fed fisheries and prawn cultures. The rest of the wetlands is free from human interference and hosts a greater amount of biodiversity compared to similar wetlands in the state. Fragmentary records of different species inhabiting these wetlands suggest that insect diversity at both taxonomic and ecological level is very high (IWMED, 2004). This includes dipterans like mosquitoes and chironomids and the Hemipterans, particularly the belostomatids and the notonectids (NANDI et al., 1993; KHAN and GHOSH, 2001). Controphic chironomid and the mosquito larvae share the belostomatids and notonectids as predators Internat. Rev. Hydrobiol. 92 2007 3 242-257

The genus Zygeilla is being reported for the first time in India in this paper. Previously one species melanocrania was placed erroneously in the gents Araneus. But our examination has revealed that it should be placed in the genus Zygeilla. Gravely collected this species from Barkuda Island (Chilka Lake), Orissa and deposited in Zoological Survey of India, Calcutta. We have got another new species of this genus, namely Zygeilla indica, which is described and illustrated in this paper.

A new genus, Neoschidium was erected with the type genus, Neoschidium phasma (Distant). It was earlier described under Ghilianella Spinola 1850 as G. phasma Distant and later under Schidium Bergroth 1916 as Schidium phasma (Distant) by Bergroth (1916). Because it exhibits characters not only of Ghilianella and Schidium but also intermediate specific characters that are not found in both the genera, the type genus Neoschidium phasma (Distant) is redescribed with additional taxonomic details, morphometrics, and illustrations. It is also recorded for the first time from India.