If you see a numbered butterfly, post it online immediately!

This year, Guangzhou has experienced the longest summer on record, and people can still go out in short sleeves until mid-November[1]. On November 19, the cold front finally arrived, and it started to drizzle. I was relieved that the temperature had finally dropped, but at the same time, I felt that it was a bad luck because I was supposed to participate in butterfly monitoring on that day.

Tiger butterfly, October 22, Baiyun Mountain, Guangzhou | ChanIm

It is best to choose a warm and sunny day to see butterflies. Butterflies are cold-blooded animals, and their body temperature changes with the environment. They need to bask in the sun to get heat. Halfway through the monitoring, we didn't see many butterflies, but the rain was getting heavier. We had to hide at a rest area in the park to avoid the rain and talked about the monarch butterflies in North America.

Monarch butterflies are world-famous for their epic migration . American nature writer Edwin Way Teale once wrote in Autumn Fields: "They flow like an endless river of insects, unfailingly, for hours." In fact, such a spectacular sight also exists on this side of the Pacific Ocean: China also has long-distance migratory monarch butterflies, but we still don't know where they go .

Butterfly flying across the ocean

There is a popular saying that "a butterfly cannot fly across the ocean", but a few butterflies can make long-distance flights across the ocean. The most famous of these is the monarch butterfly (commonly known as the monarch butterfly). Every October, hundreds of millions of monarch butterflies set out from Canada, fly thousands of kilometers to the mountains of Mexico to spend the winter, and then migrate north again in the spring of the following year.

Overwintering monarch butterflies, dozens can gather on a single twig | Steve Corey, Wikipedia

Common migratory butterflies in southern China include the orange tiger butterfly (Danaus genutia), the blue butterfly (Tirumala limniace), and several species of the genus Euploea. The butterflies overwinter as adults, and their adult lifespan is longer than that of other butterflies, with the highest record reaching 7 months. They have to migrate all the way south before the cold front to successfully overwinter. On the way of migration, if there are mountains with good environment, vegetation and water sources, they will rest in groups in the valleys that are leeward, and at first glance, they look like a mountain full of dead leaves. The Tang Dynasty Lingnan Fengwuzhi "Beihu Road" records "wooden leaves turning into butterflies", which is probably referring to the spectacular scene of clusters of butterflies taking off at the same time.

Blue butterfly, November 23, Shenzhen Futian Mangrove Park | Maya Blue

In North America, scientists have been studying the migration of monarch butterflies for 80 years. Today, we know that monarchs travel a route that stretches from Canada in the north to the mountains of central Mexico in the south, a distance of 3,220 kilometers.[2] In Asia, Japanese researchers have confirmed through tagging and release that the longest recorded migration distance of the great silk butterfly (Parantica sita) is 2,400 kilometers.[3] In Taiwan, purple monarchs migrate back and forth between their wintering grounds in Maolin, Tainan, and Taipei. However, in mainland China, the migration routes and wintering locations of these butterflies remain unknown.

Tracking migrating butterflies

Chen Xichang, former director of the Butterfly Professional Committee of the Entomological Society of China and honorary director of the Entomological Society of Guangdong Province, began studying butterflies in the 1980s. In 2005, he heard about the migration of the monarch butterfly from Taiwanese butterfly conservationist and documentary director Zhan Jialong, and began to lead students to mark the monarch butterflies and issued an appeal through local media, asking everyone to contact them if they found a marked monarch butterfly.

The marking of butterflies is somewhat similar to the ringing of birds. There are two ways to mark butterflies: one is to write the number on the wings of the butterfly with an oil-based marker, and the other is to stick the label on with glue. This is a time-consuming and laborious task. "I work with a dozen students, and the maximum number of butterflies we can release at a time is only one or two thousand," said Chen Xichang.

After more than ten years of attempts, Chen Xichang never received a response. Compared with Taiwan, the mainland's coastline is too long, and migratory butterflies of different species may be scattered in different places for wintering, and there are too few enthusiasts participating in the observation . Chen Xichang said: "What we saw in Shenzhen and Zhuhai were mainly blue-spotted purple butterflies and magic purple butterflies. We thought they would fly to Hainan Island, but the main butterflies in Hainan Island are not these two, but double-standard purple butterflies, jealous purple butterflies, and dark purple butterflies, which are rarely seen here. So, the butterflies in Hainan must not have come from Shenzhen." Chen Xichang speculated that some butterflies may have gone to an unnamed island in the South China Sea, but no one knows the answer.

Blue-spotted purple butterfly, November 23, Shenzhen Futian Mangrove Park | Maya Blue

In his observations year after year, Chen Xichang felt that migrating butterflies were becoming increasingly hard to find . He recalled that in 2012, he could still see about 20,000 to 30,000 migrating butterflies in a valley in Shenzhen. The next year, he saw only a few thousand, and the third year saw even fewer. From the fourth year on, he never saw any. The butterfly larvae that used to be easy to see in Guangzhou Baiyun Mountain are no longer to be found, but the host plants are still there. He speculated that this trend is related to global warming.

The decline in monarch butterflies is part of a larger trend of declining numbers of butterflies and other pollinating insects . Too much heat or rain can directly kill larvae. Climate also has complex effects on the distribution and metabolites of host plants, threatening the survival of some species. In addition to climate change, insects are also impacted by habitat loss and excessive use of pesticides. A review article cited thousands of times evaluated the conclusions of 16 studies and pointed out that insect populations have declined by 45% in the past four decades . [4] In 2022, the World Conservation Union (IUCN) announced that it would list the migratory monarch butterfly (Danaus plexippus plexippus) on the Red List of Threatened Species. [5]

Monarch butterfly (male) | Wikipedia, Derek Ramsey

Nature in the cracks of the city

Perhaps, compared with the migration routes of the monarch butterfly, the survival status of the butterfly population is more urgent and more immediately feasible. Chen Xichang has now retired and gradually withdrawn from field surveys. His student Jia Ci and several other insect enthusiasts founded Nature Fold, which conducts butterfly monitoring with the support of public welfare organizations such as Friends of Nature, and organizes public welfare science activities, hoping to let more people know about the butterflies around them.

The butterfly monitoring method is not complicated: select sample lines and divide sample sections through preliminary investigations, and then patrol along the sample lines regularly to record the butterflies seen . Before the monitoring began, someone asked how to identify them. Jiaci said: "Generally, if I can see the common butterflies in Guangzhou, I can recognize them." When he encountered a group that was difficult to identify, such as the gray butterfly, or wanted us to observe the details, he would wave the insect net, skillfully catch the butterflies in his hands, show us the different angles of the wings, and then let them fly away.

Observing the Central Ringed Nymph | ChanIm

I tried to appreciate the different flying postures of butterflies like bird watching. In this season, the most common butterfly in Guangzhou is the Annunciation White Butterfly, which flutters lightly like petals in the wind. In contrast, the Central Ringed Nymphalidae flaps its wings more vigorously, sometimes spreading its wings flat for a short glide. The small gray butterfly often appears in the bushes. The front of its wings is shiny blue-purple, and the back is low-key gray. When it moves, it looks like a flashing piece of colorful paper.

A butterfly landed on Mikania micrantha, November 24, Xunfenggang, Guangzhou | ChanIm

Xunfeng Mountain is an urban park at the junction of Guangzhou and Foshan. Invasive plants such as Mikania micrantha and Bidens pilosa can be seen everywhere in the park. This sample line is about 3 kilometers long and it takes 3 hours to monitor once. This is just a tiny slice of the entire monitoring project. To scientifically evaluate the survival status of butterflies, continuous and detailed monitoring data is needed, "at least five or ten years."

The long cycle makes the monitoring project face many uncertainties. If the monitoring environment is damaged, the previous data will lose its meaning for comparison and reference. Jia Ci has been following Chen Xichang to monitor butterflies since 2016, but due to changes in the sample line environment, personal studies, epidemic control and other reasons, the monitoring work has been intermittent. "If I could have continued from then, it would have been 8 years now."

Ecological monitoring belongs to basic scientific research work, but limited scientific research resources are not enough to support detailed investigations of each region and each group . Scientists can only give priority to some protected species and biodiversity hotspots, and rely on citizen scientists to obtain information on other common species. In the past, when information was less developed, citizen scientists in North America used email exchanges to sort out the migration paths of monarch butterflies. China's citizen science projects started late but developed rapidly, giving birth to a series of projects such as bird strike surveys, road kill surveys, and pollinator surveys. Perhaps we can optimistically believe that with the help of more developed information dissemination media, today's citizen scientists can exert greater power and ultimately reveal the mystery of the migration of native butterflies.

Stop and wait for the butterfly

Insects often receive less attention than mammals and birds in species conservation efforts, but civil society groups in many regions are taking action to give insects more space.

In Taiwan, people have erected protective nets along the cross-country highway that monarch butterflies must pass through during their migration, so that the butterflies can fly higher and avoid being swept into traffic. In the monarch butterfly wintering grounds in Maolin, local agencies encourage farmers to reduce the use of pesticides as much as possible and plant more nectar plants. [6] Research in North America has found that as long as ordinary citizens carry some milkweed seeds in their pockets and sow them in their own gardens or unmanaged wastelands, they can greatly improve the survival of monarch butterflies. [7] You can also plant some host plants or nectar plants on your balcony or in your yard . Such small plots of land can greatly help the survival of pollinating insects.

Milkweed is also a host for the native goldenrod butterfly | Wikipedia

As citizen science activities and research progress, perhaps one day we will finally uncover the mystery of the migration of white butterfly. On October 25, Shenzhen organized its first white butterfly tagging and release event, officially joining the International White Butterfly Tagging Network. [8] If you find a marked white butterfly, please try to take a clear photo, contact the relevant research institution through the information on the sticker, or post the photo on social media to solicit clues . However, just as the protection of migratory birds relies on the coordinated efforts of multiple regions and countries, the protection of migratory white butterflies may also require the same efforts.

Danaid Butterfly Research Hong Kong

I often take photos of beautiful butterflies, including the monarch butterfly, when I am bird watching, but I never realized that they might be visitors from afar. Insects give people the impression of being numerous and tenacious, but they are far more fragile than we think. Maybe one day, I will see a species for the last time, and I will not know it at that time, and I may not even be able to call out its name. How sad it would be to say goodbye in this way.

References

[1] Southern Metropolis Daily. Guangzhou officially announces the arrival of autumn, breaking the 30-year record for the longest summer! Experts once said that we should pay attention to the evolution. https://news.qq.com/rain/a/20241124A06MJ500?suid=&media_id=. <2024-11-24/2024-12-03>

[2] Monarch (Danaus plexippus). Butterfly Conservation. https://butterfly-conservation.org/butterflies/monarch. <2024-12-03>

[3] Kanazawa I, Cheng WWW, Pun HSF, et al. First migration record of Chestnut Tiger Butterfly, Parantica sita niphonica (Moore, 1883)(Lepidoptera: Nymphalidae: Danainae) from Japan to Hong Kong and longest recorded movement by the species[J]. The Pan-Pacific Entomologist, 2015, 91(1): 91-97.

[4] Wagner DL, Grames EM, Forister ML, et al. Insect decline in the Anthropocene: Death by a thousand cuts[J]. Proceedings of the National Academy of Sciences, 2021, 118(2): e2023989118.

[5] Migratory monarch butterfly now Endangered - IUCN Red List. IUCN. https://iucn.org/press-release/202207/migratory-monarch-butterfly-now-endangered-iucn-red-list. <2022-07-21/2024-12-03>

[6] Guo Hanchen. Nature’s most magical purple dancer. Taiwan Panorama Magazine. https://www.taiwan-panorama.com/zh/Articles/Details?Guid=3e7e4c6d-b331-486d-950c-b7bb95e59709&langId=1&CatId=10&postname=%E5%A4%A7%E8%87%AA%E7%84%B6%E6%9C%80%E5%B9%BB%E7%BE%8E%E7%9A%84%20%20%E7%B4%AB%E5%85%89%E8%88%9E%E8%80%85. <2016-01/2024-12-03>

[7] Landis TD, Dumroese R K. Propagating Native Milkweeds for Restoring Monarch Butterfly Habitat[C]. Proceedings of the 2014 Annual Meeting of the International Plant Propagators Society 1085. 2014: 299-307.

[8] Shenzhen Park launches first release of white butterfly and officially joins the international white butterfly release network. Shenzhen Municipal Bureau of Urban Management and Integrated Law Enforcement. https://www.sz.gov.cn/ztfw/gysy/wyk_183958/content/post_11669285.html. <2024-10-28/2024-12-03>

Author: Maya Blue

Edited by: Yellowtail Pollock

Title image source: Hong Kong butterfly research project