Butterfly Wing Scale Digital Image Gallery
Tawny Owl Butterfly
Insects in the genus Caligo, known as the owl butterflies, are very large tropical species famous for the large eyespots on the undersides of their wings. Visible when the wings are closed and held upright, potential predators often reconsider attacking something that appears so imposing. The yellow eyespots remind most observers of owl eyes, but some behavioral lepidopterists believe the butterflies mimic a toxic tree frog that resides in the same ecosystem.
Part of the family Nymphalidae, the tawny owl butterfly ranges from Mexico, through Central America, and into the Amazon Basin of South America. In flight, spectators may not be able to easily identify owl butterflies because the upper sides of their wings do not have the same dramatic eyespots that are featured on the undersides. Instead, the wing upper sides are covered in various iridescent color combinations that may aid in species recognition and in avoidance of hybridization. Additionally, ripple effects caused by the colorful wing patterns may add to the confusion of predators trying to detect the outline of their prey. Many owl butterflies in the wild are found with a piece of their hind wings missing, indicating that even if a predator is not deterred by the eye spots and wing colors, it may be fooled into attacking the wing instead of the vital butterfly body.
Female tawny owl butterflies lay groups of pinkish eggs on the undersides of banana tree leaves and other vegetation, such as plantains, parrot's flowers, and prayer plants. The voracious larvae that hatch from them can ingest incredible quantities of leaves and grow to enormous sizes of up to 160 millimeters long and 15 millimeters thick. The young, brown caterpillars are gregarious while feeding and are most active at dawn and dusk. By the third larval stage feeding is nocturnal and during the day the yellow-green caterpillars rest on the lower surfaces of leaves upon silken cushions. The agricultural pests feature evertable prothoracic organs, which emit defensive chemicals that are quite effective, even against the dreaded army ants of the Amazon. In the pupal stage, the tawny owl chrysalis is a bright yellow, which helps it blend in with surrounding ripening fruits.
Although a significant portion of the natural habitat of the tawny owl butterfly has been destroyed throughout the tropical Americas, it has been replaced in some areas with banana and plantain plantations. The tawny owl caterpillars are, however, killed in masses due to essentially unrestricted pesticide applications used to protect the economically important cash crops. Organically grown banana crops are protected from excessive larval damage by biological controls, such as parasitic wasps and mites.
Cynthia D. Kelly, Shannon H. Neaves, Laurence D. Zuckerman, and Michael W. Davidson - National High Magnetic Field Laboratory, 1800 East Paul Dirac Dr., The Florida State University, Tallahassee, Florida, 32310.
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