Biodiversity and seasonal fluctuation of aquatic and semiaquatic insects in Rashid stream, kafr El Zayat (Gharbyia governorate)

Rashid branch of Nile River is a principle stream in Kafr El Zayat (Gharbyia governorate) for drinking and irrigation to different essential crops. Five stations were selected for seasonal collection, resulted in 539 specimens, belonging to 7 orders and 22 families and 31 species. The total population density was higher during Spring (41.9%), then in Summer (25.1). Order Diptera was the most abundant (33.8%), represented by 5 families (Chironomidae, Culicidae, Ephydridae, Tabanidae & Stratiomyiidae) with the highest value during Spring season; then order Hemiptera (19.5%), represented by 5 families (Blestomatidae, Croxidae, Mesovillidae, Villidae & Notonectidae) with the highest value also during Spring season; followed by order Coleoptera (16.9%) with 6 families (Hydrophylidae, Dytiscidae, Noteridae, Hydranaeidae, Curculionidae & Staphylinidae), the highest representation was during Summer season; then order Odonata (16.7%), 2 families (Libellulidae & Coenagrionidae) , the highest representation was during Spring; order Ephemeroptera (9.5%), 2 families ( Baetidae & Caenidae), the highest value was during Spring; lastly order Trichoptera and Orthoptera each with one family during Summer and Winter respectively. Family Tridactylidae and Staphylinidae are collected for the first time from streams in Egypt. Tables, Figures, Keys, diagnosis and notes on habitat, in addition to detailed colored photographs with diagnostic features to all collected species were introduced to facilitate the correct identification that permits the utilization of these aquatic insects as bioindicators in monitoring programs for reflecting the ecological contents and pollution level of aquatic ecosystem along this stream.