1998 / 10月
Chang Chin-ju /photos courtesy of Vincent Chang /tr. by Robert Taylor
"On Orchid Island, when a big round moon is shining over the sea, entomologists start moving about in the woods, and clouds of moths dance in the moonlight."
"At Sun Moon Lake in May, a female atlas moth spreads her wings-more than 30 centimeters in span-and flies aimlessly under the yellow street lights, like a sheet of paper wafting through the air."
"There are so many species of moths, and they have more wing patterns than you can imagine. There are moths with white wings speckled all over with blue and yellow dots; there are moths with X-patterns which you never find on butterflies. . . ."
When heterocerist Yen Sheng-hung recounts his own experiences of watching moths, he seems almost intoxicated. He hopes other people's understanding of them can go beyond knowing that they are attracted to light.
People often speak in joyous tones when they use caterpillars pupating as a metaphor for life's sublime transformations. But when most people see real caterpillars "in the flesh," they are apt to shudder involuntarily and grimace with disgust.
If humans' feelings about caterpillars seem ambivalent, their attitudes towards the adult moths and butterflies which caterpillars turn into are even more contradictory.
When a large number of moths appear in one place, they are suspected of being a "swarm of pests," but a similar gathering of butterflies is generally regarded as a "marvelous sight," except perhaps by a few farmers who hate them for the damage they do to crops. People even raise them on special butterfly farms.
In Yellow Butterfly Valley near Meinung in Kaohsiung County, during the Japanese occupation the Japanese planted Siamese senna (Cassia siamea) for wood to make rifle butts. These trees attract large numbers of lemon migrant moths (Catopsilia pomona), but once the caterpillar swarms have stripped all the leaves from the senna trees, their numbers also fall, allowing the trees to recover again. The caterpillars also attract many kinds of birds. Thus an interesting ecological cycle has emerged which repeats itself over periods of three to five years.
Yellow Butterfly Valley has been designated as part of the area to be flooded by the planned Meinung Reservoir, and it has also suffered continuous encroachment from inappropriate land clearance for agriculture, causing the number of butterfly species, and their populations, to decline. These events have prompted conservationists both inside and outside Taiwan to call on the government to pay heed to changes in the local ecology.
People are scared of caterpillars, yet they look with loving eyes upon the butterflies which emerge from the chrysalises after caterpillars pupate; as for moths, their name in Taiwanese dialect means "mucky butterflies."
Yen Sheng-hung, who has been interested in Lepidoptera since childhood and who holds a master's degree from the Department of Biologic and Life Sciences at National Sun Yat-sen University, is well aware of people's prejudice against moths. On specimen-gathering field trips, he often hears children insist that they have come to catch butterflies, not moths, and many people appear greatly disappointed on learning that a particular kind of caterpillar will pupate into a moth rather than a butterfly.
Yen Sheng-hung says that moths have long been cast in the role of "witches of the night," supposedly with poisonous scales on their wings, and bodies which are fat and swollen compared with nature's "dancing girls," the butterflies.
The reasons behind people's disdain for caterpillars and moths are complex, but for Yen Sheng-hung, who is an expert in the taxonomy of Taiwanese Lepidoptera, what lies behind the different treatment accorded butterflies and moths is people's lack of knowledge about moths and their deep-seated misconceptions about them.
"Taiwan may have 8000 moth species, but so far only 5000 have been named." Professor Yang Ping-shih of NTU's Department of Entomology, who introduced Yen Sheng-hung to the world of insects, says there are still thousands of moths in Taiwan which have not yet been described or named. "At the moment it is nothing unusual for researchers to publish descriptions of ten to 20 new species a year."
Yen, who has done entomological research with many biologists, is Taiwan's leading Lepidoptera taxonomist. He has recorded and described many moth species previously unknown to science. But for Yen, pleasure in researching Lepidoptera clearly does not lie solely in arduously categorizing them and identifying the differences between them.
Yen finds the process by which butterfly and moth larvae are metamorphosed into adults more amazing than an alien mutation. He describes how within a larva's body there are clusters of cells called "imaginal discs" (from "imago," the adult form of an insect). While the pupating larva is in a state of "dormancy" in its cocoon, these discs suddenly begin growing rapidly and replace the larval cells-"just as if there were aliens hidden in a person's body which suddenly came squirming out and usurped the person's original form."
Hawk moth or hummingbird?
When it comes to the adult insects which emerge after metamorphosis, Yen, with his deep understanding of moths' natural history, naturally does not share most people's preference for butterflies.
In its comparison of butterflies and moths, the Encyclopedia Americana states: "There is no single prominent aspect of their morphology or ecology which suffices to distinguish between them." However, "the moths form the greater part of the Lepidoptera, yet the species most familiar to man are some of the more colorful diurnal (dayflying) butterflies."
Are colorful diurnal Lepidoptera all butterflies? Under a banner headline, a newspaper once announced Taiwan's latest ornithological "discovery": "Hummingbirds Seen in Taiwan!" But closer inspection of the photographs revealed the supposed hummingbirds to be hawk moths (family Sphingidae), which usually appear around dawn and dusk. With their long proboscises extended, flapping their wings as fast as hummingbirds as they sucked nectar from flowers, it is not surprising they fooled people.
Moths are not necessarily nocturnal, but are they all less beautiful than butterflies? Beauty and ugliness are matters of subjective judgment, but Yen Sheng-hung has something to say about this: in his "objective" opinion, there are so many moth species that at least in terms of their colors and patterns they are more diverse, and there are many arrangements of markings which do not occur on butterflies. In fact, Yen even regards butterflies as types of moths. He explains that within the taxonomic structure used in the past, moths and butterflies were assigned to different sub-orders on the basis of individual characteristics such as differences in the morphology of their antennae. But in the taxonomy now widely accepted, the butterflies are assigned to various families in the Subsection Bombycina, on the basis of their general morphology and genetic characteristics. Taxonomists "should be thinking about the evolutionary relationships between different species and groups of species, not racking their brains over whether a particular species is a butterfly or moth," says Yen.
Silkworms are moth larvae too
But when people vilify moths and call them all kinds of names, he does feel a need to set the record straight. For instance, people have the idea that all moth caterpillars have poisonous bristles which are harmful to humans. And after a podocarp plantation in Nantou County was devastated by inchworms, various newspapers repeated the baseless assertion that these moth caterpillars-which are diurnal and do not have poisonous bristles-"secrete a corrosive fluid from their bodies."
Of the 5000 moth species already identified in Taiwan, the owlet moths (family Noctuidae) and inchworm moths (family Geometridae) account for over 2000. None of their larvae have poison-secreting glands among their defense mechanisms. "Everyone seems to forget that silkworms are moth larvae too, and they don't have poisonous bristles!" laments Yen Hung-sheng. He says caterpillars are renowned for their camouflage skills-imitating the shapes and colors of their surroundings-because little creatures which "have no bristles, no poison and don't move very fast" can only protect themselves by developing ways to conceal or disguise themselves.
In the more than 100 families of moth species, those whose larvae bear toxic bristles capable of causing an allergic reaction in humans are only a small minority. Taiwan has more than 80 species of lymantriid moths (members of the family Lymantriidae), which do secrete poisons, but few of them are easy to find in the wild. Although Yen Sheng-hung has caught countless insects over the years, there are many rare lymantriid moths which he would like to study but simply cannot find.
With reference to the recent incidents of caterpillars causing allergic reactions among schoolchildren, Assistant Professor Li Mei-hui of NTU's Department of Geography notes on an Internet website that the caterpillars involved very rarely use their poison glands to directly attack enemies. After people come into contact with their poisonous hairs, the usual symptoms are allergic pain, redness and swelling; the caterpillars are not as dangerous as hornets or centipedes.
"People overlook how many moth species there are, and what a small proportion of them the ones people notice account for," says Yen Sheng-hung. Incidents of caterpillars defoliating large trees are far from being the whole story of moths' complex and diverse world.
The diversity of moth species
"There are very many amateur lepidopterists who have amassed vast amounts of information about butterflies, so researchers needn't feel too isolated," comments Yen. Also, he says, butterfly research has a relatively long history in Taiwan, so quite a large body of reliable data has been accumulated.
But what about moths? A small number which are agricultural pests have been studied in detail, but for the remaining 90% of species, people still don't even know what plants they feed on, and what parts they eat. When one compares the amount of research devoted to butterflies with that done on moths, a serious imbalance is apparent. Yen, who reads and collects large quantities of information about insects, says this means there is all the more scope for researching moths, and all the more reason to observe them.
Moths' natural histories display far greater diversity than those of butterflies. The thousands of different moth species utilize all kinds of natural resources, and their larvae may live in water, on land or above ground; they may bore into wood, soil, or the crevices in rocks, or live as parasites in other organisms; apart from eating tender leaves, moth larvae also break down underground stems, fallen leaves, ferns and even decaying meat. In Hawaii, there is even a group of inchworm moth species whose larvae specialize in catching and eating fruit flies, which are a major agricultural pest. Some moths are active by day, but the majority are nocturnal. They occupy a broad range of "ecological niches," and are found in literally every part of the forest.
Every moth family has its own special characteristics. Most ancient organisms can only be understood by studying fossils in rocks tens or hundreds of millions of years old, but the moth families Micropterigidae and Neopseustidae have already existed on this earth for over ten million years, and in Taiwan they can still be found from Fushan and Wulai in the north to Kenting in the south, and from the coasts to high in the mountains. The mouth parts of these primitive moths' adult forms still include functional chewing mandibles, rather than the sucking proboscises of other moths. They evolved from earlier trichopteroid insects (caddis flies), and have retained the latter's mouth structures.
Recently in Western biological circles there has been a great deal of interest in researching insects' sensory perception. Moths of the family Noctuidae (owlet moths) have the most highly evolved hearing organs in the form of "tympanal organs," which help them avoid being caught by bats. This seems even more amazing than the bats' echolocation ability itself.
A little-loved field
What distinguishes moths from other insects? What are their characteristic modes of life and bodily structures? "There are some general principles, but there are also huge numbers of exceptions and variations. They are living things, so they are very hard to reduce to a common denominator. Perhaps their very diversity is what they have in common," says Yen Sheng-hung.
But among the many people attracted to biological research, there are few who, like Yen, choose the field of entomology, and despite the huge number of moth species, still fewer people who research them. Their unpopularity is compounded by the general perception of them as "unclean" and "poisonous."
Even those people who do study moths do not always seem interested in learning more about them. Students studying the control of agricultural pests and diseases learn about such pests as the cluster caterpillar (the larva of Spodoptera litura, an owlet moth), corn borers (Ostrinia spp.) and the larva of the diamond-back moth (Plutella xylostella). But when asked if they know which species in the large Spodoptera genus were not pests, and whether they have observed the habits of their adult insects, many just shake their heads.
Leafing at random through a Japanese entomological journal, it comes as a surprise to see descriptions of nine newly named Taiwanese moths. From the point of view of establishing a comprehensive international database of natural resources, there is nothing wrong with overseas scholars collecting, describing and naming Taiwanese species, if it is not simply to satisfy their own need to publish. But the question is, what can we do ourselves?
Each insect a world of its own
On Mt. Shou in Kaohsiung City, there is a sight which stops many people in their tracks: beside the footpath stand Ehretia resinosa trees with their inverted-cone-shaped crowns and their gray bark speckled with little dark dots. With the approach of winter, their leaves rapidly fall, but when spring comes around they burst into bloom with little white flowers which attract not only bees and flies, but also black-and-white-striped caterpillars that shuttle back and forth between the flower buds. They look as if they are all gathered for a meeting, but each is also busily spinning threads of silk which it attaches to leaves to pull them together into shelters. The fine filaments also allow the caterpillars to travel all over the trees without having to worry about being blown away by the wind or washed off by the rain. They go on in this way day by day until they are ready to pupate. Then they crawl onto the trees trunk or neighboring plants, and spin cocoons of different colored silk according to their surroundings. From these cocoons they will finally emerge as concealer moths (family Oecophoridae) with silvery wings covered in small black spots.
The swarm of caterpillars continues until early summer, but what about the poor Ehretia resinosa trees? After a discussion on the Internet, Yen Hung-sheng and his fellow students at National Sun Yat-sen University posted the following answer: "Don't worry-once the caterpillars are gone, the trees will grow new leaves and flowers, and under the ample summer sun and rain of the north slopes of Mt. Shou they will continue to grow strong and set seed."
Nor do they forget to remind us: When spring comes around again, remember to go and look at the Ehretia resinosa -and the caterpillars!
Lepidopterist Yen Sheng-hung has no particular preference between butterflies and moths, but widespread misconceptions about moths make him feel the need to "stand up" for these much-maligned insects and help people discover what interesting creatures they really are.
"Guess who!" This isn't ET, but a little moth with feather-like antennae. (courtesy of Yen Sheng-hung)
Lacking either deadly weapons or intimidating size and strength, hawk moths have no choice but to disguise themselves as dead leaves. But this one still couldn't escape the beady eye of the human photographer. (courtesy of Yen Sheng-hung)
Are moths ugly "witches of the night"? Not to be outdone by butterflies, the dayflying helicia zygaenid moth (Erasmia pulchella hobsoni) flaunts its beauty in the full light of day. (courtesy of Yen Sheng-hung)
"I won't come out, whatever you say!" A bagworm-the caterpillar of a bagmoth (family Psychidae)-wraps itself in a pouch of silk camouflaged with fallen leaves and dry twigs. It moves itself and its bag around using its mouth and front legs.
Many people like to raise silkworms, but few remember that they too are moth caterpillars, although they are neither ugly nor poisonous. Our picture shows silk cocoons at a silk farm formerly operated at Chihshang in Taitung County by the Land Bank of Taiwan.