Bloodsucking insects, such as mosquitoes ("Culicidae"), black flies ("Simuliidae"), and botflies and deer botflies ("Oestridae", specifically, the reindeer warble fly ("Hypoderma tarandi") and the reindeer nose botfly ("Cephenemyia trompe")), are a plague to reindeer during the summer and can cause enough stress to inhibit feeding and calving behaviours. An adult reindeer will lose perhaps about 1 litre (about 2 US pints) of blood to biting insects for every week it spends in the tundra. The population numbers of some of these predators is influenced by the migration of reindeer. Tormenting insects keep caribou on the move searching for windy areas like hilltops and mountain ridges, rock reefs, lakeshore and forest openings, or snow patches that offer respite from the buzzing horde. Gathering in large herds is another strategy that caribou use to block insects.