Distribution and Occurrence of Four Caddisfly Species in Genus Macrostemum along Nan River in Nan Province, Thailand

Abstract

Database of Thai caddisfly still lacks a record of Nan River – one of four main rivers in northern Thailand. The pioneer study on four interesting species in genus Macrostemum (M. dohrni, M. floridum, M. indistinctum and M. midas: Hydropsychidae, Trichoptera) was done along Nan River in Chiang-Klang and Tung-Chang Districts, Nan Province, Northern Thailand. Eight sampling sites were monthly set portable light traps for collecting adult caddisfly (both male and female) and recorded environmental factors and riverbed habitats for a year (November 2016 – October 2017). M. dohrni and M.indistinctum were rare in the study (4% and 1% of all specimens,respectively), which their spatial distribution and temporal occurrence were showed. M. indistinctum abundance had the different seasonal pattern from other species that were mostly dominant in hot season. M. floridum was common (86% of all specimens) and their male and female had significant significant negative relationship to the relative air humidity (P<0.05). The life cycle of the studied species was univoltine. Although Nan River highly found river modification and agricultural activities, the nutrient concentrations were still low and habitats were available for other aquatic insects that suitable for further environmental and taxonomic studies.