Population dynamics of mosquito immatures and the succession in abundance of aquatic insects in rice fields in Madurai, South India.

Abstract

Studies on the breeding pattern of mosquito immatures and the successional changes in the abundance of aquatic insects were conducted in rice fields near Madurai, south India. The population of late (III/IV) larval instars of culicines peaked on Day 28 and pupae (Culex tritaeniorhynchus, Cx. pseudovishnui and Cx. vishnui) peaked on Day 9 after transplantation, whereas the population of late (III/IV) larval instars of anophelines peaked on Day 19 and pupae of Anopheles subpictus and An. vagus on Days 7 and 9 respectively, after transplantation of paddy. A total of 14 families (consisting of 17 subfamilies) of aquatic insects belonging to six different orders, Coleoptera, Diptera, Ephemeroptera, Hemiptera, Anisoptera and Zygoptera were collected during the study period and the abundance of each group of insects is discussed in detail. The Shannon-Weaver Diversity Index, applied to study the diversity of different groups of aquatic insects, showed a clear pattern in diversity of surface predators, bottom predators and non-predators of mosquito immatures. The multiple linear regression model reveals that notonectid adults, coenagrionids, libellulids and veliids act as important predators of mosquito immatures in rice fields.