| Owl butterflies | |
|---|---|
| Caligo martia | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Insecta |
| Order: | Lepidoptera |
| Family: | Nymphalidae |
| Subfamily: | Morphinae |
| Tribe: | Brassolini |
| Genus: | Caligo Hübner, [1819] |
| Type species | |
| Caligo eurilochus Cramer, 1775 |
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| Diversity | |
| Some 20 species | |
| Synonyms | |
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Butterflies in the genus Caligo are commonly called owl butterflies, after their huge eyespots, which resemble owls' eyes. They are found in the rainforests and secondary forests of Mexico, Central, and South America.
Owl butterflies are very large, 65–200 mm (2.6–7.9 in), and fly only a few metres at a time, so avian predators have little difficulty in following them to their settling place. However, the butterflies preferentially fly in dusk, when few avian predators are around.[1] The Latin name may possibly refer to their active periods. Caligo means darkness.
Some owl butterflies form leks in mating behavior.[2]
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There are some 20 species in this genus, which can be divided into 6 groups that might constitute subgenera. Some species are of uncertain placement with regard to these groups, however:
The underwing pattern is highly cryptic. It is conceivable that the eye pattern is a generalized form of mimicry. It is known that many small animals hesitate to go near patterns resembling eyes with a light-colored iris and a large pupil, which matches the appearance of the eyes of many predators that hunt by sight. The main predators of Caligo are apparently small lizards such as Anolis.
According to the Batesian mimicry theory the pattern on the wings of Caligo resemble the head of a predator like a lizard or an amphibian. It should deter predators while resting, feeding, mating or emerging from the pupa.
The role of eyespots as antipredator mechanisms has been discussed since the 19th century. Several hypotheses are suggested to explain their occurrence.[4] In some butterflies, particularly Satyrinae (such as the Gatekeeper Butterfly and the Grayling), it has been shown that ocelli serve as a decoy, diverting bird attack away from the vulnerable body, and towards the outer part of the hindwings or the forewing tip.
Research of Stevens et al. (2008), however, suggests that eye-spots are not a form of mimicry and do not deter predators because they look like eyes. Rather the conspicuous contrast in the patterns on the wings deter predators.[5] In this study, however, the influence of surrounding forms, like the head region of a predator, was not tested. Also the question why animals evolved such complex imitations of other species is left.