Two Possible Caterpillar Mimicry Complexes in Neotropical Danaine Butterflies (Lepidoptera: Nymphalidae)

Abstract Caterpillar mimicry is surprisingly scarce, despite many examples of apparently defended, aposematic species. Here, we describe two possible examples of caterpillar mimicry in two tribes of the Neotropical Danainae: Danaini and Ithomiini. The first example, from the Caribbean island of Hispaniola, includes two subtribes of Danaini: Danaus plexippus (L.), Danaus gilippus (Cramer), Danaus cleophile (Godart) (Danaina), Anetia briarea (Godart), and Anetia jaegeri (Ménétriés) (Itunina). The first two widespread Danaus species have unusually dark phenotypes on Hispaniola, which we suggest are the result of mimicry with endemic Caribbean danaines. The second example, from the upper Amazon of eastern Ecuador, involves four subtribes of Ithomiini: Forbestra olivencia (Bates) (Mechanitina), Hypothyris fluonia (Hewitson), Hypothyris semifulva (Salvin) (Napeogenina), Ithomia amarilla Haensch (Ithomiina), Hyposcada anchiala (Hewitson), Oleria sexmaculata (Haensch) (Oleriina), and Pseudoscada florula (Hewitson) (Godyridina). Hyposcada illinissa (Hewitson) (Oleriina) is a possible additional member. This mimicry ring shows a color pattern known only from the upper Amazon, with the caterpillar having a yellow body and bright blue anterior and posterior segments, and this pattern has clearly evolved at least four times in the Ithomiini. We suggest that precise mimicry among caterpillars may be rarer than among adult butterflies because of a lack of sexual selection to drive the initial evolution of bright colors in larvae. We also suggest that the evolution of warning colors in protected caterpillars is more difficult than in butterflies, because a novel, conspicuous caterpillar is less able to avoid capture than the more agile adult.