Experimental Studies of Mimicry. 5. The Reactions of Toads (Bufo terrestris) to Bumblebees (Bombus americanorum) and Their Robberfly Mimics (Mallophora bomboides), with a Discussion of Aggressive Mimicry

Laboratory experiments described in this paper support the hypothesis of Batesian mimicry of bumblebees (Bombus americanorum) by asilid flies (Mallophora bomboides). Seven Southern toads (Bufo terrestris) were used as caged predators. 2. Experimental toads which initially attacked bumblebees learned to reject them on sight alone. They then also rejected mimics to a significantly greater extent than control toads which did not have prior experience with the bumblebees. 3. Two of the three control toads also freely are bumblebees from which the sting had been removed. This indicates that the noxious quality is the sting. 4. Field observations of the predatory behavior of the adult flies in south central Florida show that the mimetic flies prey extensively upon their bumblebee models. 5. The idea of aggressive mimicry, proposed but then discarded by Poulton, is reconsidered in the light of new evidence and it is concluded that the selective basis for the resemblance of bees by flies, in addition to being Batesian mimicry, may in part also be the visual selection resulting from the defensive behavior of the models towards the mimics which attack them.