Vanessa atalanta, the red admiral or, previously, the red admirable, is a well-characterized, medium-sized butterfly with black wings, red bands, and white spots. It has a wingspan of about 2 inches (5 cm). It was first described by Carl Linnaeus in his 1758 10th edition of Systema Naturae. The red admiral is widely distributed across temperate regions of North Africa, the Americas, Europe, Asia, and the Caribbean. It resides in warmer areas, but migrates north in spring and sometimes again in autumn. Typically found in moist woodlands, the red admiral caterpillar's primary host plant is the stinging nettle (Urtica dioica); it can also be found on the false nettle (Boehmeria cylindrica). The adult butterfly drinks from flowering plants like Buddleia and overripe fruit. Red admirals are territorial; females will only mate with males that hold territory. Males with superior flight abilities are more likely to successfully court females. It is known as an unusually calm butterfly, often allowing observation at a very close distance before flying away, also landing on and using humans as perches.
In northern Europe, it is one of the last butterflies to be seen before winter sets in, often feeding on the flowers of ivy on sunny days. The red admiral is also known to hibernate, re-emerging individuals showing prominently darker colors than the first brood. The butterfly also flies on sunny winter days, especially in southern Europe.
In North America, the red admiral generally has two broods from March through October. Most of North America must be recolonized each spring by southern migrants, but the species overwinters in south Texas.
Male red admirals are territorial and perch during the afternoon until sunset. Larger territories are optimal and subject to intrusion by other males more frequently than smaller territories. Territories tend to be oval, 8–24 feet (2.4–7.3 m) long and 13–42 feet (4.0–12.8 m) wide. Males patrol their territory by flying around the perimeter between 7 and 30 times per hour. On average, territory holders interact with intruders 10 to 15 times per hour.
When another male encroaches on a red admiral's territory, the resident chases away the intruder, often in a vertical, helical path to disorient or tire out the intruder while minimizing the horizontal distance it travels from its perch. The red admiral immediately returns to its territory after chasing off encroaching males. Time spent patrolling increases as number of the intruder interactions increases.
Patrolling behavior is correlated with warmer air temperatures, so males begin patrolling early and continue later on warmer days. Overcast skies usually led to patrolling later in the day. It is not clear whether this later start time is due to lower air temperature or a direct effect of decreased solar radiation. Another theory is that males believe it is earlier in the morning on cloudy days because of the reduced solar radiation.
