A survey on species composition of aquatic insects was conducted in seven major sites of contiguous area of Bach Ma National Park, Thua Thien Hue province. The result showed that there are 120 species belonging to 86 genera, 39 families recognized during the expeditions. Of three orders, the Ephermeroptera is the most diverse with 40 species occupying 33.33 percent
the Coleoptera with 19 species making up 15.83 percent
each of the two orders Odonata and Hemiptera has 15 species (12.50 percent)
the Plecoptera comprises 14 species (11.67 percent)
the Trichoptera has 11 species (9.17 percent) and the Diptera has 6 species (5.0 percent). Among 39 families of aquatic insects were found in this study, the Gerridae is the most diverse with 10 species occuping 8.33 percent, 10 genera occuping 11.63 percent. The family Baetfdae takes the second place with 9 species taking up 7.50 percent, 6 genera (occuping 6.98 percent)
the Heptageniiadae has 8 species (6.67 percent), 5 genera (5.81 percent). Of the total, there are 27 species and 11 genera and 2 families are newly recorded for Bach Ma area.