World’s biggest butterfly

Ornithoptera alexandrae (Rothschild, 1907), the Queen Alexandra’s birdwing, is the biggest butterfly found on the entire planet. It can only be found on Papua New Guinea, and is considered and endangered species that faces many modern threats. Here they are mainly found in the forests of Popondetta valley. The males are slender and bright iridescent blue and green, while the females are very large, have a big wing surface area and are dark in colour. It’s wingspan ranges between 140mm and 250mm – the males are in the smaller range.

A pair of Ornithoptera alexandrae. Top: the colourful male – bottom: the greyish looking female. Photographer: Bart Coppens – from the collection of Naturalis Biodiversity Centre

 Ecology
The most important aspect in the ecology of Ornithoptera alexandrae is it’s food plant. This butterfly has an intimate evolutionary relationship with several types of pipevine plants (Aristolochia, Pararistolochia)- most importantly Aristolochia dielsiana (O.C. Schmidt) M.J. Parsons-  (synonyms: Aristolochia schlechteri, Pararistolochia) which is a species of pipevine found in West New Guinea  and Papua New Guinea. For a long time it was thought to be monophagous on this host plant although since then other host plants have been determined, namely Pararistolochia alexandriana and P. meridionaliana (Parsons 1999, Matsuka 2001). Females visit these plants and deposit eggs on the underside of the leaves. These plants are often found high up in the canopy (40m). The reason they specialise in pipevines is because these plants offer the butterflies protection; pipevine plants are toxic and contain aristolochic acids – toxic compounds that discourage herbivores from eating them. However, the caterpillars are able to eat the pipevines and store these toxins inside their body, becoming toxic themselves – usually by sequestering them inside their fat bodies. Over time, the more biomass the insects gain and the more toxin they sequester, the more toxic they become. For that reason the mature caterpillars and adult butterflies have low rates of predation. Researchers think the butterflies can live for several months, even up to 3 or 6 months because most (but not all) vertebrate predators know to avoid them because of their toxicity. While predation pressure is low, the highest mortality is observed in the early life stages (eggs and young larvae) by invertebrate predators such as ants, wasps, spiders and parasites (parasitic wasps/flies) and in later stages frogs, lizards, birds, and insectivorous rodents.  Larvae take a while to develop – in the wild 107 to 131 days (Straatman 1971) was recorded, depending on the local temperatures and microclimate. After pupating, adult butterflies hatch from the naked, girdled pupa.

The imagoes of Ornithoptera alexandrae real canopy butterflies. This species avoids dense forests (even if the food plant is abundant there) and is found in open, light forests where it is easier for these large butterflies to navigate. Adults visit flowers but prefer to visit flowering plants high up in the canopy, although they (rarely) descend to feed on nectar from lower plants. It can be difficult to get a good glimpse of the butterflies because of this. Adults are infrequently seen and are usually found in low densities. While they rarely seem to stray very far from their habitat, in rare cases females have been seen migrating over grasslands. However the species has not been recorded outside of the Popondetta Plains region, apart from one high altitude population. The total area of occupancy is estimated to be under 140km² and has been fragmented into a few smaller populations- of how many isolation populations this species consists still needs to be investigated more carefully, although literature suggests this species consists of a minumum of four (4) and a maximum of six (6) isolated populations. These populations differ in altitude although most of them live in lowland rainforest (around 400m) although some populations live up to 800m+.

Threats
The future of this species is uncertain. The main threat to the existence of this species is habitat destruction. In Papua New Guinea, large parts of it’s habitat have been or are actively being destroyed: the main reasons for this are palm oil plantages and deforestation. However, rubber and cacao and urban development also play minor roles. “The main threat to the species is habitat destruction, which has been noted as early as 1971 by D’Abrera who suggested that the species is becoming increasingly rare due to collecting and cutting down of forest which destroys growth of larval food plant. Specifically, the species is threatened by habitat destruction for plantation of income-generating crops such as oil palm (Allan 1985, Collins and Morris 1985, Parsons 1992, New 2007). Cocoa and rubber plantations have also been a problem in the past; in fact as early as 1983, the species was suggested to be endangered because of its limited range and the threats to its forest habitat in the Popondetta Plain from oil palm and timber industries (Parsons 1983, Allan 1985). Overall, it has been suggested that illegal collecting is not comparable with loss of habitat as a threat (Collins and Morris 1985). There has been some forest cover loss specifically within the Popondetta region between 2001 and 2014 (Hansen et al. 2013). Very few of the forests potentially affected by threats from logging and oil palm production are protected under Category I and II levels by the IUCN (New 2016); FAO figures of oil palm plantation area in the country show increases by 72.3 % from 1989 to 2013, with 25.3 % stemming from deforestation (Vijay et al. 2016).” – IUCN RED LIST

Collecting
Ornithoptera alexandrae is a protected, endangered animal that is very popular among poachers – a well-preserved dead specimen of this butterfly can have a market value of hundreds or even thousands of dollars. Many butterfly collectors are willing to pay increasingly high prices for them.
Is this a problem?
Out of the many serious threats that are making the future of this species uncertain, collecting plays a suprisingly small role. While capturing and collecting these butterflies is illegal, it appears that poachers and collectors recieve a disproportionate amount of blame – possibly to shift the attention away from the real problems, such as their entire habitat being fragmented and destroyed for commercial gain. In that regard, collection seems to have an insignificant impact and it not at all compareable to the destruction of their habitat (Collins and Morris 1985).  This is because insect populations are able to sustain mortality of individuals – even a species like O. alexandrae with low predation pressure is easily able to keep up with the rates at which humans can capture adults. Read more about the impact of collecting here! 

So collecting them is not wrong?
This is not a justification for collecting them. Anybody caught smuggling protected species should be reported to the relevant authorties. Your personal opinions are not above the law. While there is no evidence that collecting them actually hurts their populations, still, nothing good can come from capturing them. Not only does it shed bad light on serious collectors and scientists, species that are already under pressure from so many factors should be left to recover alone with minimal interference inside the remains of their habitats. Besides, it will be a convenient scapegoat for palm oil and logging companies.

Back to Lepidoptera notes

My hand next to a pair of  Ornithoptera alexandrae.  Photographer: Bart Coppens – from the collection of Naturalis Biodiversity Centre

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