Evaluating a putative mimetic relationship between two butterflies, Adelpha bredowii and Limenitis lorquini

1. A laboratory bioassay experiment was performed in order to investigate a long‐standing putative mimetic relationship between two butterflies, the Lorquin's admiral Limenitis lorquini and the California sister Adelpha bredowii (Lepidoptera, Nymphalidae). These butterfly species are commonly sympatric in their broad distribution on the west coast of the United States. The wing colour pattern of L. lorquini differs from the patterns exhibited by its North American congeners, resembling A. bredowii instead. 2. The feeding responses of California scrub jays Aphelocoma californica (Passeriformes, Corvidae) to these prey types and a known palatable control, the buckeye butterfly Junonia coenia (Lepidoptera, Nymphalidae), were examined quantitatively. The birds usually demonstrated long handling times of A. bredowii before consumption, while L. lorquini was manipulated and consumed at the same rate as the control butterfly. The birds also exhibited feather ruffling and bill wiping after consuming A. bredowii while they did not exhibit such behaviours after consuming L. lorquini and J. coenia . 3. The birds did not discriminate between the dorsal colour patterns of the two species in a choice experiment. 4. Because A. bredowii was moderately unpalatable to the captive scrub jays and the birds were not discriminating in their choice, this suggests a Batesian mimetic relationship between L. lorquini and A. bredowii .