Surveys for natural host plants of Mansonia mosquitoes inhabiting Toh Daeng peat swamp forest, Narathiwat Province, Thailand

Abstract

Surveys were carried out monthly from April-October 2002 to examine 68 sampling sites around "Toh Daeng" peat swamp forest in Narathiwat Province, Thailand, of which 38 were known Mansonia-positive habitats and 30 were Mansonia-negative sites. The present larval surveys were qualitative owing to features of the host plants (location, distribution, and abundance), difficulties in locating and selecting the host plants in the swamp forest, and time constraints. Twenty attempts were made for each species for larvae. The presence of Mansonia larvae on each plant species was confirmed 6 times for each plant and location. Larvae of Ma. bonneae and Ma. uniformis were obtained from 18 plant species (10 families): Metroxylon sagu, Melaleuca cajuputi, Pandanus militaris, Pandanus immerses, Hanguana malayana, Typha angustifolia, Hymenachne acutigluma, Scirpodendron ghaeri, Scleria sumatrensis, Rhynchospora corymnosa, Sacclolepis indica, Cyperus babakan, Cyperus corymbosus, Lepironia articulata, Leersia hexandra, Eichhornia crassipes, Pistia stratriotes and ferns. The emergent grasses, S. ghaeri, S. sumatrensis, H. acutigluma, R. corymnosa, S. indica, C. babakan, C. corymbosus, and L. articulata, were the preferred host plants. Samples from larger trees, M. sagu and M. cajuputi, yielded low numbers of 1-7 larvae per scraping. Ma. uniformis was recovered from most of the host plants, while Ma. bonneae preferred submerged plants and was not found on the floating aquatic plants, E. crassipes and P. stratriotes. The description of modified dipper and dipping techniques are given and discussed.