What are black flies?
Black flies are small (1-3 mm), usually dark colored, biting flies with a distinctive “humpbacked” profile (see photo right). Immature, or larval, black flies develop in fast flowing streams, rivers and creeks where they cling to the undersides of rocks or debris. A few species breed in relatively slow moving water and can even be found in landscape water features. Black flies are very persistant and fierce daytime biting flies. The bite site often bleeds profusely because of a strong anticoagulant in the saliva of the fly. An itchy skin lesion usually develops at the bite site as well. Like mosquitoes, black fly females require a blood meal in order to lay healthy eggs.
