These insects almost always look alight and fly milling about in dirty open places. Flies often appear in large quantities during the day. When the sky turns dark, they are almost impossible to find, even in the dirtiest locations of trash cans. Maybe not a few who ask, where do the flies fly at night? according to one of the books that I have read, most species of flies are only active during the day. "The animals need polarized light to guide them visually", as quoted by The New York Times. When the day turns into twilight, the flies take shelter under the leaves, stems, branches, and branches of trees. In addition, they are also shelter on high grass stems or other plants. Flies usually will not spend the night on the ground, some types of insects such as mosquitoes and desert flies, usually prefer dawn and dusk as their 'working hours'.