Limenitis arthemis, the red-spotted purple or white admiral, is a North American butterfly species in the cosmopolitan genus Limenitis. It has been studied for its evolution of mimicry, and for the several stable hybrid wing patterns within this nominal species; it is one of the most dramatic examples of hybridization between non-mimetic and mimetic populations. L. arthemis can be split into two major groups, mainly based on one physical characteristic: the presence of a white band along the wings. Individuals of the northern group, called white admirals, have a conspicuous white band that traverses both the dorsal and ventral surfaces of the wing, while those of the southern group, called red-spotted purples, lack that trait as they have evolved to mimic the poisonous pipevine swallowtail (Battus philenor). Due to overlap in distribution among the two major groups, intermediates are numerous as hybridization occurs frequently.
Etymology Limenitis (Neo-Latin "of harbours", from Ancient Greek Λιμενιτις (from λιμήν, a harbour, haven) – an epithet of Artemis, goddess of the hunt and the wild) – arthemis, from Artemis.
Taxonomy and phylogenetics Limenitis arthemis is a butterfly species in the tribe Limenitidini of the family Nymphalidae. The Limenitidini are a tribe of the better known "brush-footed butterflies," as they are known to perch on hindlegs, whereas the other two forelegs are positioned curled up. These two forelegs often have brush-like hairs, which is a key identifier of the Nymphalidae. The Limenitidini consist of 25 species grouped primarily by region. The Basilarchia species group, spread in North America, includes the American white admiral species, L. arthemis, as well as L. archippus, L. lorquini, and L. weidemeyerii.
Subspecies
L. a. arthemis has the common appearance described in the description section of the white admiral. L. a. rubrofasciata has a brick-red band along the margins of the ventral hindwing, and are mainly found west of Lake Superior. L. a. astyanax has red spots on the underside of the wings, while the upperside has no white bands, but irridescent blue on the hindwings L. a. arizonensis has wings that appear similar to the L. a. astyanax, but pointier hindwings. This subspecies resides in the southwestern regions of the US.
Hybridization Limenitis arthemis is one of the most dramatic examples of hybridization within a nominal species. The two major subspecies that dominate the hybridization are L. a. arthemis (white admiral) and L. a. astyanax (red-spotted purple). The white admiral is characterized by a bright, white band on its wings, while the red-spotted purple lacks the white band, but has cooler blue-green shades on its wings. Hybridization occurs in the area across New England, southern Ontario, and the Great Lakes, also known as the "suture region". It is at these regions that the subspecies were formed.
According to one study, these hybrid zones were of secondary origin, meaning that both the white admiral and the red-spotted purple are already genetically distinct and the two diverged lineages reconnect at this hybrid area. They were able to support their claim by examining various of mitochondria DNA of the population to determine the similarities and differences of the origins of the hybrid zones and the evolution of mimicry. Another study suggests that hybridization is highly frequent in this species because similar species mate together regardless of being the same butterfly or not. For instance, the L. arthemis was found to be mating with a L. archippus butterfly in New England.
Description and identification
Limenitis arthemis is described to be beautiful and highly active. The butterfly species themselves can be divided into two major groups simply from one main characteristic, the white band on the upper wings. However, besides the look of the butterfly, L. arthemis are in constant motion. Their flights are short in duration and at low altitudes, flying only about 2 to 3 feet off the ground. When not in flight, L. arthemis are constantly walking over leaves and folding their wings. They enjoy the sun as many are found to be resting at the highest points on trees. During the short period they are at rest, L. arthemis keep their wings closed, body at a 45 degree angle upwards, and antennae straight forward. The two sexes of this species are identical except that the females are slightly larger than the males. The upperside of L. a. arthemis is mostly blackish-blue with white postmedian bands across both wings. Some individuals have a row of red submarginal spots, while others have this area being blue. The underside of the wings is a blackish color with a broad white post-median band. The basal area of both wings contains many red spots. The submarginal area may contain a row of red spots and the marginal area having bluish spots. However, sometimes the submarginal and marginal areas are just a reddish-brown color. The upperside of L. a. astyanax is very much like L. a. arthemis except it lacks the broad white bands. The forewing submarginal area will sometimes have a row of red spots. The hindwings are either a bright iridescent blue or an iridescent bluish-green. The underside of the wings lacks the white band. The basal area has several red spots. It has a row of red submarginal spots and bluish marginal spots.
Distribution and habitat Limenitis arthemis are vastly spread out throughout North America. L a. arthemis or the white admiral live on the far north side of the continent, ranging from New England and southern Great Lakes area all the way to various parts of Canada. L. a. astyanax are based further south from the New England and southern Great Lake boundary, and can be found as far south as Florida; the hybridization region is the overlapped region of New England and southern Great Lakes. These butterflies spend their days in deciduous woodlands, along the edges of the forest in shady areas, including roadsides.
Batesian mimicry
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