The Red-spotted Purple (Limenitis arthemis) is a butterfly that frequents the forests and woodlands of the Long Point Basin. It is part of brush-footed butterfly group (Nymphalidae), closely related to the Viceroy (Limenitis archippus). While dense deciduous forests are the Red-spotted Purple’s primary habitat, where is most observed, it is also occasionally found in oak savannas, meadows, and shrublands.
Description
The Red-spotted Purple is a medium to large butterfly with a wingspan of 6 to 10 cm. Females are slightly larger than males. These butterflies possess a blue or purple iridescence that forms a broad band across the posterior (back) side of both hindwings. They also have a distinctive series of red spots on the underside of each wing. Morphology widely varies across the Great Lakes Region, with two distinct morphs across the Great Lakes Region. In the northern areas of the Great Lakes region, such as Algoma District, Algonquin Highlands, and Manitoulin Island, these butterflies have a distinctive white stripe on the upper wings, and they are called White Admirals (Limenitis arthemis arthemis). In the southern regions around Lake Erie, these butterflies are properly called Red-spotted Purples (Limenitis arthemis astynax), lacking a white stripe characteristic of White Admirals. Red-spotted Purples also have bluer wings to mimic the poisonous Pipevine Swallowtail (Battus philenor). This deters predators – such as birds and other arthropods, including insects and spiders. There is a wide zone of integration where both morphs co-occur, particularly in Bruce and Grey County on Lake Huron. White Admirals are found north to the arctic treeline, whereas Red-spotted Purples occur as far south to Florida. Though sometimes White Admirals are found in the Long Point Basin, by far the dominant form of the butterfly are Red-spotted Purples.
From late May onwards, Red-spotted Purples will emerge as newly emerged adults from their chrysalis. Afterwards, their main objective is to breed. Males are fiercely territorial over areas of the forest that are most visited by females. In general, Red-spotted Purples are most often found in forests, swamps and oak savannas, but may also visit tallgrass prairies if their preferred food resources are available. Adult butterflies prefer to feed on nectar from flowers, rotting fruit, dung, and detritus. Life expectancy as an adult, Red-spotted Purple is 1-2 weeks. There are typically two broods of adult swallowtails, with the second overwintering brood emerging in July.
Red-spotted Purple butterfly eggs are deposited on the foliage of their host plants – which include cherries (Prunus sp.), willows (Salix sp.), poplars (Populus sp.), oaks (Quercus sp.), and basswood (Tilia americana). Yellow birch (Betula lutea), abundant in densely forested habitats, is especially preferred by these butterflies. Eggs hatch in around a week. The larvae (caterpillars) immediately begin feeding on the foliage, lasting around 3 weeks to fully grow. However, if the caterpillar is part of the second (autumn) brood, caterpillars will undergo hibernation starting in October. These caterpillars will hibernate until May, when they emerge, undergoing a feeding frenzy on newly emerged foliage, rapidly accumulating sufficient energy to pupate into a chrysalis. To deter predators, Red-spotted Purple caterpillars mimic the appearance of bird droppings, which are (as expected!) unpalatable to most species. The cycle begins again when the adult butterflies 10-14 days later.
Fun facts
- While they strongly resemble swallowtails, especially the Spicebush Swallowtail (Papilio troilus) and Pipevine swallowtail, which they mimic, a key identifying feature of the Red-spotted Purples are that they lack “tails” on their hindwings that many swallowtail species possess. They are also smaller than swallowtails on average.
- The red spots on the wings more often appear orange to observers, while the iridescence is usually blue rather than purple. Maybe “Orange-spotted Blue” would be more accurate!
- Red-spotted Purples prefer feeding on soil minerals, tree sap, rotting fruit, dung, or even carrion over the nectar of flowers, which they only occasionally visit!
Written by Matthew Palarchio, HBSc in Environmental Sciences, Western University.
Photo Credits (L-R): Chrissy McClarren and Andy Reago (Red-spotted Purple on flower), Matthew Palarchio (Red-spotted Purple exposed hindwings), Matthew Palarchio (White Admiral), Matthew Barbour (caterpillar)
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