__________________________________ Bull. Ent. Soc. Egypt, 83, 2006 (231-245) STUDIES ON THE DISTRIBUTION, DIVERSITY, AND ACTIVITY PERIODS OF SPECIES BELONGING TO SUBFAMILIES GYMNOMYZINAE AND EPHYDRINAE (DIPTERA: EPHYDRIDAE) FROM EGYPT By ALY A. EL-MOURSY 1 , MAGDI S. EL-HAWAGRY 1 , FATHY H. NEGM 2 , AND AYMAN M. EBRAHIM 2 1 Entomology Department, Faculty of Science, Cairo University 2 Classification Research Department, Plant Protection Research Institute (Received 20-8-2006) INTRODUCTION Species of the family Ephydridae are often prominent members of aquatic and semi-aquatic environments. This family attracted great interest of workers because of the extreme abundance of certain species in marginal habitats including highly saline and alkaline lakes and pools, and crude oil pools. The fresh water species have elicited more attention in recent years, but most studies have been concerned primarily with elucidation life histories (Eastin & Foot, 1971; Deonier, 1972; Busacca & Foot, 1978; Deonier & Regensburg, 1978). Many species are well known for their ability to endure extreme habitat conditions. As salt-influenced biotopes, larvae of some Ephydra spp. are found in water basins near the red sea beach where the water has a concentration salinity reaching 38% NaCl; on the other hand, adults were found resting on the water surface. Lindroth (1931) reported that the shore fly larvae could be found in water with temperature of 53°C-55°C. Other shore fly species were known from Hot Springs (Tuxen, 1936). Some shore fly species are adapted also to low temperatures as Scatella stagnalis, which is known from Alaska, Northwest Territory of Canada, northern Greenland and the arctic parts of Europe. Most ephydrid species show a distinct tendency in their reaction to the hygric factor. The great majorities are hygrophilous, needing a moist substrate for their development; some develop in moist soil or need vegetation for their mining