The Gulf fritillary or passion butterfly (Dione vanillae or Agraulis vanillae in other taxonomies) is a bright orange butterfly in the subfamily Heliconiinae of the family Nymphalidae. That subfamily was formerly set apart as a separate family, the Heliconiidae. The Heliconiinae are "longwing butterflies", which have long, narrow wings compared to other butterflies.
Dione vanillae is most commonly found in the southern areas of the United States, specifically in many regions of Florida and Texas. The species was moved to the genus Agraulis in 1835 by Boisduval & Le Conte. A phylogenetic analysis reported in 2019 placed Agraulis as a sub-genus of Dione.
Description
In its adult form, the gulf fritillary is a medium-sized butterfly that has extended forewings and a wingspan range of 6.5 to 9.5 cm. This butterfly exhibits sexual dimorphism as females are typically distinctively larger in size than males. The underside of the wings is brown and speckled with silvery white dots. In contrast, the top surface layer of the wings is deep orange in color with black streaks running across. In addition to the size difference between the two sexes, females are usually darker in color and are more marked with black streaks as compared to the males.
Geographic range
Gulf fritillaries are found primarily in the southern parts of the contiguous United States, from Florida and Georgia to Texas and California. However, this butterfly’s range can extend from the Southern United States into parts of Mexico and Central America and sometimes as far as parts of South America. They are also found in Hawaii.
Propagation
Oviposition
The process of oviposition in gulf fritillaries begins with the female butterfly flying low and slightly above the vegetation (most likely the typical host plants like Passiflora incarnata or Passiflora lutea) and lasts until the female pauses above an individual plant. Then, the female makes contact with the host plant by landing; the female then deposits an egg to complete the process of oviposition. The driving factor behind what causes the female to oviposit on or near the host plant is most likely due to the certain chemical composition of the specific genus of the host plant. Once the female recognizes the chemical composition (by using the antennae), the female will oviposit. The spikes are soft to the touch and serve the purpose of scaring predators.]]
thumb|Gulf Fritillary caterpillar, Florida, January 2021
In appearance, the larvae are dark orange with small black spines protruding outward from the body. The larval stages of gulf fritillaries include five instars, each with a varying timeframe. After the eggs hatch, the new larvae eat the egg casings for food. Eventually, the larvae will transition either to consuming other eggs or parts of the host plant for nourishment. Throughout the first three instar stages, the larvae primarily consume the leaves and feed away from the leaf margins of the host plant. How much of the leaf and how deep into the layers the larva will eat depend on the type (i.e. thickness or thinness) of the leaf in question. Throughout the last two instar stages, the larvae mainly consume the leaves and feed at the leaf margins. Throughout this food acquisition process, the degree to which a specific leaf is eaten before it is abandoned in favor of another newer leaf largely depends on whether food is in plentiful or scarce supply. The average duration of the larval stage is between 11 and 16 days depending on the temperature.
Defense against predators
Both male and female gulf fritillaries possess certain defensive glands located on their abdomens that serve as a defense mechanism against predators, especially avian predators such as birds. When the butterflies sense danger in the area or are suddenly disturbed, these glands emit a distinct and obvious odor which is composed of several different types of chemicals, such as 6-methyl-5-hepten-2-one and hexadecyl acetate. The summation of these chemical compounds released from the glands leads to birds preferentially avoiding the gulf fritillaries in favor of other prey. In some cases, gulf fritillaries can sometimes be subjected to competition and fighting from other butterfly species, such as Heliconius charithonia vazquezae and Dryas iulia moderata when those species have breeding populations in similar areas and within the same geographic range.
Mating
Courtship behavior
The general process for a typical courtship interaction begins when a male flies and lands near a perching female, who is most likely perched on a host plant, such as several species of the Passiflora genus. Once the male has landed, the male assumes a position next to the female with their heads together and with their bodies aligned at a 45-degree angle. At this time, the male engages in a specific action called the wing clap display in which the male continuously claps its wings open and closed. During this time, the antennae of the female are placed between the opening and closing wings. After the male ceases wing movement, the male butterfly will move into a position that facilitates genital contact with the female. The average duration of the copulation process including the wing clap display is approximately 11 seconds.
Female and male interactions
Pheromones
The release of pheromones by the male gulf fritillaries plays a critical role in the mating and courtship process. Studies have shown that the males possess specific structures on their dorsal wings that engage in the production and eventual release of chemical pheromones. It is likely that pores that exist on the wings of the male butterflies transport the pheromones to the surface where the chemicals can be released and can then affect the females. The use of pheromones in the mating process relates to the idea of mate choice.
Nuptial gifts
Along with chemical pheromones, the presence of nuptial gifts plays an important role in the mating and courtship process. During the physical act of copulation, males transfer nutritious materials to the females. These extra nutrients given to the females can be used by a female to her advantage during the process of oogenesis. The use of nuptial gifts in the mating process, especially when females mate with multiple males, relates to the idea of female choice in deciding egg fertilization.