Nycteribiidae of the true fly superfamily Hippoboscoidea are known as "bat flies", together with their close relatives the Streblidae. As the latter do not seem to be a monophyletic group, it is conceivable to unite all bat flies in a single family.They are flattened, spiderlike flies without eyes or wings, and are seldom encountered by general collectors, as they almost never leave the bodies of their hosts. Both males and females take blood meals, thus they qualify as real parasites.