Australian painted lady
|Australian painted lady|
|Species:||V. (C.) kershawi|
|Vanessa (Cynthia) kershawi
Cynthia kershawi McCoy, 1868
The Australian painted lady (Vanessa kershawi) is a butterfly that is mostly confined to Australia, although westerly winds have dispersed it to islands east of Australia, including New Zealand. There is debate surrounding the taxonomy of this species. Some believe that the Australian painted lady should be a subspecies to the painted lady due to the similarity in lifestyle and behavior. Furthermore, the painted lady is found around the globe but Australia is the only location in which it varies enough to be considered a separate species. However, due to the distinct genitalia of the males, and variation in coloration, many others consider the Australian painted lady to be a separate species. During spring, adult butterflies migrate south in large numbers from northern states of Queensland and New South Wales. In order to find mates, male Australian painted ladies exhibit territorial behavior, which involves a male perching on vegetation in a sunny spot on a hilltop, waiting for females to fly by. Despite urbanization and invasive plants altering its habitat, populations of Australian painted ladies have not been significantly impacted by these changes.
- See also painted lady#Distinguishing features
The Australian painted lady is remarkably similar to the painted lady (Vanessa cardui). It is differentiated by its smaller size, rarely exceeding 2 inches across its wings, and the blue coloration at the center of the four eyespots on its hind-wings. Its body is dark brown, almost black, all over, except the tips of the antenna which are white.The base of the wings are brown, which turns into a brick red coloration, broken by bands of black. The tip of the are black with four white dots running from the apex of the wing, and a white bar extending from the leading edge of the forewing. The hind-wings have four round eye-spots at their base, with a blue center for at least three. The underwings are almost identical to the upper-wings, except the base of the underwings is brick red rather than brown. The Australian painted lady's coloration allows it to blend in effectively with the ground. Males and females look almost identical. The ovum is translucent green in color and barrel-shaped with 13-15 vertical ribs. Right before hatching, the black head and grey tinted body appear through the shell. The larva is grey with pale yellow stripes along each side of its body, yellow dots, and has rows of branched spines covering its body. Its head is typically brown or black, and the caterpillar grows to approximately 3 cm. The pupa is brown with darker markings, and four pairs of metallic silver or gold dots.
The Australian painted lady belongs to the family Nymphalidae. It belongs to the genus Vanessa, which compromises 22 species, which are strongly migratory. The Australian painted lady is similar to the near-cosmopolitan painted lady V. cardui, so it considered by some to be a subspecies of that The painted lady butterfly. However, throughout its range, the painted lady does not exhibit much variation, but the male genitalia of the Australian painted lady is distinct form that of the painted lady, which suggests that it is a separate species. The Australian species' four ventral eyespots are less clearly defined, and it always sports at least three (often four) conspicuous blue pupil spots on each dorsal hindwings' eyespots. V. cardui has either a few tiny pupil spots, or more often, none at all.
The Australian painted and the painted lady have very similar lifestyles and behaviors, but the Australian painted lady lives in an arid and stressful environment. A recent study has shown that the Australian painted lady coloration could be induced in painted lady butterflies by injecting the larvae with stress inducing hormones and subjecting them to lowered temperatures. This demonstrates the phenotypic plasticity, or the tendency for visible traits to vary with changing environmental conditions, of the painted lady butterflies. It also suggest that the painted lady is the ancestral form, and environmental stress slowly drove speciation by adaptation into the Australian painted lady. In other words, the Australian painted lady most likely evolved form the painted lady due to the environmental conditions in Australia.
The Australian painted lady's distribution is restricted to Australia. The closely related Vanessa cardui is found throughout the rest of the world, therefore the two species have an allopatric distribution. Within Australia, the Australian painted lady is commonly found throughout southern Australia, below the Tropic of Capricorn line. It is uncommon to find this butterfly in Queensland, and it is completely absent from the far north of the country, in the tropical rainforests. Although it is most common in Australia, it has also become common throughout New Zealand following periodic migrations across the sea, from Australia. Since the butterflies do not reproduce or overwinter in New Zealand, they are only considered an established species in Australia. Within its range, it is found in urban areas.
The life cycle of the Australian painted lady lasts approximately 53 days in the summer months. The females lays her eggs in the center of the leaf of a food plant. The eggs are green and hatch in about three days. As a caterpillar, the Australian painted lady is only active at night, during which its main activity is feeding. During the day, it hides in a curled leaf or at the foot of a food plant. The pupa hangs vertically from the underside of the leaf of a food plant, and the duration of the pupal stage is approximately two weeks.
The Australian painted lady typically uses the native Australian everlastings and other daisies as a host and food plant. However, it also feeds on several introduced species, including Capeweed (Arctotheca calendula), Scotch Thistle (Onopordum acanthium), and Lavender (Lavendula officinalis). The adults feed on the nectar of flowers.
Eggs have being recorded on Arctotis, Chrysanthemum (Asteraceae family) and Scotch Thistle (Cirsium vulgare), but the resulting larvae do not survive past the first instar on these plants. Successful larvae have been observed on Capeweed (Cryptostemma) and Cudweed (Gnaphalium). There are limited results, usually causing malformations on Everlasting daisies (Helichrysum bracteatum) and (Helichrysum bellidioides). If there are not enough leaves, then they will eat flowers. Individuals reared on Capeweed (Cryptostemma) produces foul-smelling imagos. Other foodplants have being recorded in Australia, but do not appear to be used in New Zealand.
Mating system and territoriality
The Australian painted lady's mating system evolved due to a highly dispersed female population. Food and oviposition sites are abundant as females feed on a wide range of host plants; therefore, females do not cluster around hotspots of resources. This tendency makes it impossible for a male to defend the entirety of a female's range. Therefore, the best strategy for males is to defend a territory in which females are likely to travel. Females will generally only visit male territories when they are receptive, with the purpose of copulating. However, when an abundant food source attracts a significant number of females, males no longer exhibit territoriality and are seen searching for mates in areas where females are clustered.
In order to defend a territory, the males exhibit perching behavior starting in the mid to late afternoon until dusks. Some individuals are able to reclaim the same territory multiple afternoons in a row. The longest period of time recorded in which one male defended the same territory was 3 days. The males choose sunny spots on hilltops, which females are likely to travel through. If no hilltops are available, the males will wait in channels in the vegetation that would funnel wandering females towards the male. The perching male sits and waits, scanning the sky for any moving object. Periodically, he will execute a patrol flight in order to get a better picture of the surrounding area. When the male spots a moving flying object, he will fly directly towards it. If it is a male, the resident male will chase him off his territory. If it is a female, the male will chase the female, more slowly and less aggressively than with an intruding male, away from the perch site. The pair will land and copulate, which can last more than an hour.
Observations of the Australian painted lady migration, in the scientific literature, date back to the 1960s. In 1963, there was a large migration of the Australian painted lady in a southeasterly direction, which took place from late August to late September. It was characterized by the species becoming suddenly common in certain areas where the species had previously been sparse. That year was noted to have been unusually wet in Australia. This could be a trait shared with the closely related Vanessa cardui, which migrates in Europe during the wet season. More recent studies have shown that that the Australian painted lady migrates south in the spring and summer, and north in the autumn and winter.
Migrating butterflies often have a smaller and lighter body size that allows the butterflies to fly longer distances. Additionally, these butterflies tend to have larger wings to body ratio. Temperatures and day length have been found to influence development. When larvae were exposed to short days and cool temperatures (20°C), similar to conditions found in the spring, the larval development was accelerated. This produced small adults with a low body weight, ideal for migration. A similar phenomenon occurred when the larvae were exposed to longer days at warm temperatures (30°C), conditions similar to those in the late summer. Seasonal changes could trigger the development of spring and fall body forms that are ideal the migration patterns described above.
During periods of large migration in Australia, and with the possible help of strong wings, the Australian painted lady migrates across the sea to New Zealand. Multiple occurrences of this butterfly in New Zealand were reported in the 1960s. In the spring of 1968, they appeared on the western coast of New Zealand near the sea, and were unusually abundant. It is unlikely that the species is established in New Zealand, as there were no instances of larvae or adults hibernation through the winter. Although some individuals reproduced and laid eggs, the larvae only developed to the first instar before development stopped. The same phenomenon occurred in the late summer 1969, and coincided with a gale force westerly wind. This evidence suggests that the butterflies observed in the spring of 1968 and the summer of 1969 were the result of a new migration from Australia, and not the offspring of a generation of previously migrated painted ladies. The migration of butterflies and moths from Australia is not uncommon in the summer months with strong winds.
Response to a changing environment
Fragmented habitats due to urbanization, as well as disturbances to the environment from humans and introduced species are harmful to most butterflies. Additionally, there are threats to local vegetation such as recreation, trampling of vegetation, fire regimes, and introduction of plant pathogens, which bring about changes to local plant community. Distribution of butterflies depends heavily on the site characteristics and the density of that species' host plant. Changing plant composition changes the distribution of most butterflies's range, isolating them to pockets, where the vegetation is ideal. Because of the variety of host plants utilized by Australian painted lady butterflies, it has not been significantly impacted by these changes. It has been found to use some of the specieses of carduine thistles as a host plants in New South Wales, as species, which is invasive to Australia. Australian painted ladies use the plants as a hosts during their larval stage, and as food sources. However, they inflict little damage to the plant.
Vanessa cardui, compare hindwing eyespots
|Wikimedia Commons has media related to Vanessa kershawi.|
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