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

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Abstract
Laboratory experiments were carried out which support the hypothesis of Batesian mimicry of bumblebees (Hymenoptera; Apidae) by robberflies (Diptera; Asilidae). Seven southern toads were used as caged predators. Three experimental toads which initially attacked bumblebees learned to reject them on sight alone. They then also rejected mimics to a significantly greater extent than 4 control toads which did not have prior experience with bumblebees. Two controls also freely ate bumblebees from which sting had been removed, indicating that the sting is the noxious quality. Field observations of predatory behavior of adult mimetic flies showed that they feed extensively upon their bumblebee models. This led to a reconsideration of the idea of aggressive mimicry. It was concluded that the selective basis for the resemblance of these flies to bees, in addition to being Batesian mimicry, may in part also be visual selection resulting from the defensive behavior of the models towards their mimics which attack them.