Batesian mimicry is effective when:
In Batesian mimicry, an edible or harmless mimic gains protection by resembling a defended model. The system is negatively frequency dependent: predators maintain avoidance when encounters with genuine noxious models are more common than rewarding encounters with mimics. If mimics become too abundant, predators increasingly discover that the shared signal can be attacked safely, weakening protection for both forms. Predator education is also essential because avoidance usually develops after experience with the model or inherited responses shaped by such encounters. A model population larger than the mimic population therefore preserves signal reliability, whereas equal or mimic-dominated frequencies undermine the deception. A careful interpretation retains the assumptions of the underlying model and avoids extending it beyond available evidence. Within those assumptions, the keyed concept gives the most consistent account of the biological pattern and its expected outcome. This interpretation follows ecological definitions based on effects on fitness, energy flow, behavior, and population performance. It also shows why superficially similar alternatives can represent different mechanisms once the direction of benefit, harm, or resource transfer is considered.
Ref: Evolutionary Analysis, Herron & Freeman, 5th Ed., Ch. 10