Studies on the taxonomy of aquatic heteropteran bugs (order: Hemiptera) from selected habitats of Kerala and their efficacy as biocontrol agents on mosquito larvae of Culex quinquefasciatus say

Abstract

Kerala represented a wide variety of flora and fauna and many aquatic ecosystems. Aquatic insects are abundant in most freshwater habitats and often exhibit high diversity. Among them, Suborder Heteroptera has a diverse group of bug species, and they are adapted to various habitats like terrestrial, fully aquatic, and semi-aquatic. Aquatic and semi-aquatic bugs are also called as “water bugs”. They perform several critical roles in ecosystem functioning by virtue of their numerical abundance, taxonomic diversity, and trophic levels. This research study is mainly concentrated on the taxonomy of aquatic heteropteran bugs from selected habitats of Kerala and the biocontrol experimental study of selected predators of water bugs on the larvae of Culex mosquitoes. The investigation was carried out from the year 2016 to 2020. The water bugs were collected from a total of 109 locations of 14 Districts in Kerala and 12 different aquatic habitats were selected for this research study. Minimum number of samples were collected by using simple random sample method. Then they were sorted and transferred to air tightened bottles containing 70% alcohol. All the collected samples were identified at species level with the help of taxonomic keys, monographs, and published literatures. A total of 65 species belongs to 34 genera and 14 families of 3 infraorders were recorded during the study. Each species was taxonomically described, and the locations were mentioned. Among these, 30 species were new records from Kerala. In which, 13 species were reported for the first time from South India. The distribution map of 30 new recorded species from Kerala was generated with the help of ‘QGIS’ software. Identification key of all the explored infraorders, families, genera, and species of the water bugs were provided. The biological control experimental study of selected species of predatory water bugs such as Laccotrephes ruber Linnaeus, 1764, Ranatra filiformis Fabricius, 1790, and Diplonychus rusticus Fabricius, 1781 on the species of disease-causing filarial vector, Culex quinquefasciatus Say, 1823. The above said predators were very commonly found and they were collected from the selected aquatic habitats of Palakkad District for this study. The mosquito larvae were sufficiently reared by using the water mixed with decayed vegetable leaves in a plastic bucket and kept for one week in the household areas and the preys were collected from this. Both predators and preys were identified with the help of standard taxonomic keys and published literatures. The experimental data was statistically analysed with the help of the computer software “SPSS 22” and the efficacy of three selected water bugs were assessed. The predatory efficiency was found more by the predator L. ruber Linnaeus, followed by D. rusticus Fabricius, and R. filiformis Fabricius. The present research study was proved and confirmed that the water bugs were the predacious carnivores and biocontrol agents of mosquito larvae, C. quinquefasciatus Say.