Current Issue

Bug of the Week is written by "The Bug Guy," Michael J. Raupp, Professor of Entomology at the University of Maryland.

Beautiful but stinky: Gulf fritillary, Agraulis vanillae


The gorgeous Gulf fritillary butterfly harbors a couple of unpleasant surprises for any would-be predator.


Flowers of the passion vine are among the most magnificent in the plant world.

The blossom of the passion fruit vine is one of the most gorgeous in the angiosperm world. Exotic flavors of the passion fruit are used around the world add zest to ice cream, cheesecake, and mixed drinks. Passion fruit is rich in vitamin C and lycopene and consuming this delicacy is said to sooth a queasy stomach, according to Andean lore. As Bug of the Week continues its winter sojourn to warmer parts of the globe, our next stop is Belize where we recently met termites, ants harvesting leaves and protecting their home, brush-footed butterflies, and chemically defended swallowtails. This week we meet the beautiful Gulf fritillary which uses leaves of passion vine as food for its young.



Even on a cool wet morning in Belize, the Gulf fritillary seems unafraid to rest in full sight of predators.


In a vacant lot in the center of Belize City, I had the opportunity to enjoy the antics of the Gulf fritillary as it darted across the meadow seeking nectar from lantanas and other weedy blossoms. The Gulf fritillary is a broad ranging species taking up permanent residence from Argentina to the southern United States. During summer, peregrinations take it as far north as San Francisco on the west coast and New Jersey on the east coast, but in autumn this vagabond travels south to the warm climes of the Floridian peninsula to spend the winter.

Striking contrasts of orange body and black spines may serve as a warning to predators to avoid making a meal of Gulf fritillary caterpillars.

Like other members of the longwing butterflies that consume passion vine as their larval food source, the Gulf fritillary has remarkable adaptations. As a group, passion fruit plants are protected from most leaf-munching caterpillars and other vegan insects by a veritable witch’s brew of highly toxic chemicals including alkaloids, a family of toxins that includes strychnine and nicotine, and cyanogenic glycosides, chemicals that release cyanide upon entering the body. However, the Gulf fritillary and other members of its clan, including the zebra longwing we met in a previous episode, turned the tables on passion fruit plants, bypassing the noxious defenses, and feasting with impunity on their leaves. Some species of longwings sequester cyanogenic glycosides from their food and others manufacture these compounds on their own, presumably for defense. The striking orange and black coloration of the adult butterfly warns vertebrate predators not to mess with this beauty. In addition to any plant derived defenses, the beautiful Gulf fritillary has one more bit of chemical trickery to help keep predators at bay. Glands on the abdomen produce and release a concoction of complex esters when the adult butterfly is disturbed. This stinky defensive fluid dissuades predators such as birds from making a meal of these dazzling butterflies. Beautiful but stinky is a recipe for success for the Gulf fritillary.       


Like its cousin the Gulf fritillary, a zebra longwing caterpillar consumes large quantities of passion vine leaves each day.


References used in the preparation of this Bug of the Week include ‘Caterpillars of Eastern North Americ’a by David L. Wagner; ‘Coevolution of Animals and Plants’ by Lawrence Gilbert and Peter Raven; ‘Gulf Fritillary Butterfly, Agraulis vanillae (Linnaeus)(Insecta: Lepidoptera: Nymphalidae)’ by Jaret C. Daniels; and ‘Novel chemistry of abdominal defensive glands of nymphalid butterfly Agraulis vanillae by Gary N. Ross,  Henry M. Fales, Helen A. Lloyd, Tappey Jones, Edward A. Sokoloski, Kimberly Marshall-Batty, and Murray S. Blum. We thank the hearty crew of BSCI 339M, ‘Mayan Culture and the Interface between Tropical Rainforests and Coral Reefs’, for providing the inspiration for this Bug of the Week.