The study of Lepidoptera, the order encompassing butterflies and moths, often highlights extreme variation in size. The pursuit of the absolute size record leads directly to a single, undisputed champion among the world’s approximately 17,500 butterfly species. This article details the identity, unique biology, and precarious existence of this magnificent, record-holding insect.
Identifying the World’s Largest Butterfly
The title of the world’s largest butterfly belongs to Queen Alexandra’s Birdwing (Ornithoptera alexandrae). The size record is based on the female’s wingspan, which significantly exceeds that of any other species. Female wingspans consistently measure between 25 and 28 centimeters (10 to 11 inches), with exceptional specimens reaching up to 30 centimeters, or nearly a full foot across.
The species displays striking sexual dimorphism, meaning the female is not only larger but also dramatically different in appearance from the male. The record-holding female is predominantly dark brown, featuring white and cream-colored markings arranged in chevrons on the forewings and a submarginal line of yellow triangles on the hindwings. Her body is cream-colored, and she can weigh up to 12 grams, which is an enormous mass for a butterfly.
In contrast, the male is smaller, typically boasting a wingspan of about 16 to 20 centimeters, and is far more vibrant. His wings are long and angular, displaying iridescent, metallic-looking blue-green and black colors, while his abdomen is bright yellow. This species was first discovered in 1906 by collector Albert Stewart Meek in Papua New Guinea and was named the following year in honor of Alexandra of Denmark, the wife of King Edward VII.
Specialized Biology and Unique Life Cycle
The birdwing’s size is supported by its specialized diet and extended life cycle. The larval stage is exclusively dependent on the poisonous pipevine plant, a local species known as Aristolochia schlecteri (or similar Pararistolochia species). The female lays her large eggs on the leaves of this specific vine, which provides the only food source for the emerging caterpillars.
The caterpillar, black with fleshy red tubercles, consumes the plant’s toxic compounds, sequestering them in its body tissues without being harmed. This process renders the growing larva and the subsequent adult butterfly distasteful and toxic to most potential predators, a defense mechanism known as aposematism. The larval stage is notably long, lasting approximately four months, allowing the caterpillar to accumulate the massive body mass necessary for its final transformation.
The entire life cycle, from egg to adult butterfly, spans a lengthy period of five to seven months, significantly longer than most temperate butterfly species. The adult butterfly, or imago, emerges with a slow, heavy flight pattern, characteristic of a species that advertises its toxicity. Males patrol their forested territories, often high in the canopy, searching for newly emerged females, which may live for up to six months as adults.
Geographic Limits and Conservation Status
The Queen Alexandra’s Birdwing has one of the most restricted geographical distributions of any butterfly, being endemic solely to the Northern Province of Papua New Guinea. It is confined to a limited area of coastal rainforest near the town of Popondetta, including the remote Managalas Plateau. This small, fragmented range makes the species extremely vulnerable to environmental changes.
The butterfly’s habitat was severely reduced in the 1950s by the catastrophic eruption of nearby Mount Lamington, which destroyed a significant portion of its lowland forest home. Today, the primary threat is ongoing habitat destruction driven by commercial interests. Large tracts of the lowland rainforest are continuously being cleared for logging operations and the expansion of plantations, particularly for palm oil.
Due to this severely limited range and continuing habitat loss, the species is classified as Endangered by the IUCN. It is also listed on Appendix I of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). This designation prohibits all international commercial trade in the species, protecting it from the historical threat of collectors seeking high-priced specimens.