Butterflies and Moths
This is one of the most popular orders with amateur entomologists because it contains many large and beautifully colored insects. Lepidoptera means, "scaly-winged." Of the approximately 135,000 species in this order, 24,000 are butterflies. Butterflies and moths are very much alike. In fact, butterflies descended from moths. Generally speaking, butterflies are colored more brightly than moths. The reason for this is associated with the time of day when each group is active. Moths usually are nocturnal while butterflies typically are diurnal. Butterflies, being day-fliers, rely on their bright colors to attract individuals of the opposite sex. Because moths are night fliers and because it is more difficult to perceive color in reduced light intensities, moths do not rely on sight to find the opposite sex but use odor or sex pheromones instead.
An additional difference between butterflies and moths is the shape of their antennae. Butterfly antennae typically are thread-like and usually terminate in a small knob or ball. In many cases moth antennae are much more elaborate, frequently appearing comb-like. This difference may be due to the fact that moths rely on odor to find the opposite sex and therefore need more elaborate (efficient) antennae.
The mouthparts, or proboscis, of adult butterflies and moths consists mainly of two "soda straw" appearing structures (modified maxillae) that are capable of being rolled up or unrolled when feeding on liquids such as nectar or drinking water.
KILLING BUTTTERFLIES TO SAVE THE RAINFORESTS
As previously mentioned there are many amateur entomologists around the world who collect and buy butterflies and other insects for their private collections. There are people who would object to this practice, suggesting that it is the use of nature for one’s own personal pleasure. And it is well documented that butterflies and other insects are beginning to disappear from many areas, including the tropics of the world. However, it is also documented that the collecting of insects has had little, if any effect, on the total population in any given area. The disappearance of plant and animal species from temperate and tropical areas of the world can be attributed to the destruction of their habitat. The authors estimate that the cutting of one large rainforest tree may kill a million or more insects.
There have been many different projects attempting to save the rainforests of the world. Unfortunately, most of these have had little, if any effect on this decimation. In most cases the underlying reason for these failures seems to stem from human encroachment into these areas in attempts to acquire capital gains or merely provide the essentials of survival. Two of the main practices that result in rainforest decimation are forest clearing for conventional farming practices and logging. It is difficult to condemn either of these practices because typically both provide money and food for the individuals who inhabit or own the forests.
of Papua New Guinea instituted one program that has had considerable success.
They established a central agency, the
idea behind this program was to make the forest of
15A. A box of Ornithoptera birdwings that were farmed by the natives of
Papua New Guinea.
Estimated collector value, $1,000.
The natives raise enough money from this practice to buy the few western goods they desire and to pay the taxes for their children’s schooling. The forest remains intact for hunting of food and there is little need to turn to agriculture. Papua New Guinea's people primarily are hunters. The insect population in this island country has changed little since this program was initiated. It is too bad that this can’t be said for other tropical countries. Actually butterfly farming is becoming more common in many tropical areas of the world because it is a solution that is good for the people of the rainforests and for those interested in maintaining what remains of the world's forests.
Although there are several species of silkworms, Bombyx mori is the one used almost universally for silk production (Figure 15B). The discovery of the use for this species for commercial silk production occurred in China about 2,700 B. C. Chinese legend states that a great prince directed his wife to study the silk moth and its potential for making cloth or silk. She not only discovered the means of raising Bombyx mori on mulberry leaves but also the manner of reeling the silk strand from the cocoon to make thread. She was later given an honored name, Seine-than, or "The Goddess of the Silk Worm". Silk production subsequently spread through China and became a very valuable commodity throughout the world. The secret of silk production became a very closely guarded secret in China with the leakage of this secret punishable by death.
Figure 15B. An adult male silkworm moth.
By the first century A. D., the origin of silk was still protected by the Chinese. Early writing of the Roman Virgil speculated that silk was produced from the fuzz of leaves. Considerably later (300 AD) the secrets of sericulture were leaked from China into Japan by a Chinese princess who carried the eggs of the moth and seeds of mulberry in her headdress and later into Rome by a monk who carried the same in a hollow staff.
With China’s monopoly on silk production broken, importation from China became less and less. In 877 A. D. a rebel chief raided the city of Canfu, the center of foreign silk production in China, killed all of its inhabitants, destroyed all the mulberry leaves and silk moths and imposed very high taxes on foreign trade. This stopped foreign trade on silk in China for over one-half century. However, by that time silk production had become fairly widespread in the world and these actions had little effect on the price of Chinese silk. Asia still remains the center of silk production today with countries like India, Thailand and China leading the way.
Silk production on a commercial basis has been attempted on several occasions in the United States with limited success. In early colonial times, silkworm rearing for the good of the British Empire was widespread. In fact, in some areas, it was illegal not to raise them. The French had been doing quite well with silkworm rearing and competition between Britain and France was in full bloom. After the American Revolution, sericulture was still practiced by the new American society.
In 1831, J. H. Cobb published a manual on sericulture, which was purchased and distributed to the U. S. Congress. This created great interest in the U.S. and eventually led to what is known as the Morus multicalis craze. Anticipating immediate riches, thousands of people bought large parcels of rather expensive land and established huge plantations of mulberry trees of the above species. Because of massive over planting and subsequent frost destruction of most of the trees, these ventures still failed. However, because of the Civil War, cotton was not readily available in the northern U.S. Consequently, there was still interest in developing some type of fabric industry in the north.
Thus, in 1869, Professor E.L. Trouvelot imported from France into Massachusetts some eggs of the gypsy moth with the idea of finding a less host-specific moth (the silkworm only feeds on mulberry) that could produce silk. Trouvelot's efforts to replace Bombyx mori with the gypsy moth were a failure. The silk was poor quality and the silkworms were hard to rear. Either during or after his experimentation, some caterpillars escaped. Now this moth is spread throughout most of the United State and its caterpillars are considered one of, if not the most, serious defoliating pests of our forests.
The silkworm possesses a pair of modified salivary glands, which are used to produce silk for encasing the pupal stage in a cocoon (Figure 15C). These glands produce a clear proteinacous fluid, which hardens into a silken thread when it comes into contact with air. Over a 4-day period the last instar larvae produces the silken cocoon for pupation. The caterpillar makes approximately 300,000 figure eight movements with its head while producing over 900 meters of a continuous silken thread to make the cocoon. This thread must be unwound prior to the emergence of the adult moth. The pupae are typically killed by heat, electrocution or microwaves and subsequently the cocoons are soaked in hot water prior to unwinding the silken threads from the cocoon. Single threads are combined to form yarn for weaving.
Figure 15C. The cocoon of silkworm pupae, the source of silk fibers.
Silk production is time intensive. The larvae feed solely on mulberry leaves and a larva eats 50,000 its initial weight in leaves to reach adulthood. It takes approximately 1,500 cocoons to produce one silk dress. The nourishment of 1,500 caterpillars (Figure 15D) requires approximately 110 pounds of mulberry leaves. World silk production has doubled in the last 30 years in spite of the availability of man-made fibers. The current world production is about 160,000,000 pounds, requiring almost 100 billion worms.
Figure 15D. Silkworm caterpillar feeding on mulberry leaves.
There are countless references to butterflies and moths in the mythology of many cultures throughout the world. This is due primarily to these insects’ beauty, power of flight and complete metamorphosis. In the interest of brevity we will restrict our discussion to butterfly and moth mythology in North America.
The sheer beauty of butterflies plays an important part in a legend of the Papago Indians. According to this myth the creator felt sorry for babies when he realized that their destiny was to become old, wrinkled, fat, weak and blind. Consequently, he gathered beautiful colors from sunsets, rainbows, clouds, flowers and the sky and placed them in a bag, which was presented to children. When the bags were opened, butterflies flew out, enchanting the children who had never seen anything so beautiful. If that wasn’t amazing enough, the butterflies sang as they emerged from the bags but the songbird became jealous because the butterflies were not only beautiful but could also sing. Consequently the creator withdrew the butterfly’s ability to sing.
In a Motorway legend of the Navajo, a bisexual god named Begochildi was leader of the butterfly people and serviced the sexual need of both the male and female butterflies. However, when Begochildi decided to leave the country, the butterfly people decided to commit incest rather than marry outsiders. This made the butterfly people go wild, which is today manifested in the tendency of moths to wildly fly to a flame or light. The Mothway legend is to the Navajo an explanation why sibling and clan incest is forbidden.
The Blackfeet believed that butterflies bring dreams to us. A mother would paint the symbol of a butterfly on a small piece of buckskin and tie this in the baby’s hair when she wanted the baby to go to asleep. At the same time she would sing the baby a lullaby to call the butterflies to put the baby asleep. It was felt that if you looked long enough at the soft gentle flight of the beautiful butterfly it would calm you to sleep.
Many of the Hawk or Sphinx moths, such as the death head moth, emerge as adults from their pupal cases several hours before embarking on their virgin flights in the evening. Immediately prior to flight, these young moths exude a few drops of clear red fluid (a by-product of pupal metabolism) called meconium. In some cases, during peak seasonal emergence, it almost appears as though it is raining blood from the sky. In Europe this situation of "blood" falling from the sky has lead to the myth of a sign of impending war or other disasters.
A few species of butterflies exhibit long seasonal migrations. Two notable U.S. species are the monarch and painted lady butterflies. The painted lady is an orange and black butterfly, which occurs throughout much of the world (Figure 15E). In Western North America this species spends most of the winter months building up its population with the caterpillars feeding on thistle in Northern Mexico. In the spring, as their host plants begin to dry up, the adult butterflies begin their northward migration, which eventually reaches Oregon, Washington, and sometimes as far north as Canada. Individual butterflies do not typically fly the 2000-mile trip but lay their eggs on host plants along the way. It may take a few generations and several weeks to complete the trip.
Figure 15E. The painted lady butterfly, a well-known migratory species.
Upon reaching their destination, a few generations are completed in the north. In late fall a few adults migrate back to northern Mexico to complete the yearly cycle. Some years this spring movement is scarcely discernible. Other years the migration is huge and it is almost impossible to look outdoors at any one time without seeing several of these butterflies. The limiting factor appears to be the availability of the thistle host in Mexico. If the winter rains in this area arrive early and there is an abundance of this host, the migration will be heavy.
The Monarch butterfly has a similar migration (Figure 15F). However, because it is a native to the southern states of the U.S., Central and South America, its migration can be several thousand miles from South America into northern Canada. As do all butterflies, they fly during the daylight hours and rest during the night. It is not unusual for entire huge trees in the migratory path of these butterflies to be so heavily covered with resting butterflies that their leaves cannot be seen.
Figure 15F. The monarch butterfly is
perhaps the most studied butterfly in the world.
The exact mechanism of how migrating insects navigate is not well understood. It is possible, at least in some cases, that they follow prevailing winds.
Being larger and therefore more visible insects, there are a number of predators that feed chiefly on butterflies and moths. This is especially true with butterflies because they are brightly colored and are day fliers. As one might suspect, these insects have developed a vast array of defensive mechanisms. These mechanisms are by no means limited to the adult stage. Many moths, upon depositing their eggs, scrape scales off their bodies and wings to cover the eggs—thus making them less visible to predators and parasites.
Caterpillars (larval stage of butterflies) typically are plant feeders. Most of those that feed on leaves are green in color, incorporating the chlorophyll from the leaves into their bodies, thus giving themselves a significant degree of camouflage. In addition, a few caterpillars bear urticating, or stinging, hairs (Figure 15G). A classic example of this is the saddleback moth caterpillar. This caterpillar is adorned with long stinging hairs. I once collected this species in northern Thailand. I had read about urticating hairs but had never had the "pleasure" of experiencing their effect. Being interested in experiencing this I picked the caterpillar out of my net with my fingers. Bad idea! The resulting effect was much quicker and more painful than that of a hornet sting. It was almost as though a severe electrical shock shot through my hand. Now that you are an educated entomologist, it should come as no surprise that this caterpillar is distinctly marked with a bright red head with most of the body a brilliant green encompassing a large red spot and fringed with a gold outline for good reason. Great warning colorations. To make matters worse, that evening we were driving up Doi Suthep (a mountain) looking for walking sticks, tarantulas, giant millipedes or any other creature we might pick up crossing the road in our headlights. After catching about 6 12-inch millipedes we stopped for what I thought was another millipede. Instead it was the biggest caterpillar I had ever seen (at least 9 inches). Without thinking that this was a pretty hairy critter, I picked it up and, of course, the resulting effect was about twice as bad as that of the saddleback. To this day we have not been able to identify this caterpillar to even family level, although I have the pleasure of knowing it is soaking in alcohol in our museum.
Figure 15G. Top-Left. An unknown species of caterpillar illustrates bright warning coloration and urticating hairs located on the back area of the abdomen (looks like small sea urchins). Top-Right. A puss caterpillar one of the better known caterpillars with urticating hairs. Image courtesy of CDC. Middle-Left. Image Courtesy of Peter Chew, Brisbane Insects. Middle Right Saddleback moth. Image courtesy Gerald Lenhard, Bugwood. Bottom Hag Moth caterpillar. Image courtesy Jerry Payne, USDA, Bugwood.
Because the pupal stage of most Lepidoptera is found below ground, it is not readily available to most predators and parasites. However, butterflies are actively sought by many. It might be thought that their bright coloration would be a distinctive disadvantage for survival. However, the wings of butterflies typically have bright colors on the upper side while the underside is dull in coloration (Figure 15H). As a result, when a butterfly is in flight, the alternate flashing of bright and dull results in what is referred to as the flicker effect. Apparently most predators need to focus in on their prey prior to capture and the flicker effect impedes this ability—thus giving the butterfly an added advantage to escape. Also, when butterflies are at rest, they usually hold their wings folded together—thus not exposing the bright colors and drawing unwanted attention.
Figure 15H. A Papilio ulysses butterfly from
Indonesia illustrates the
brightly colored upper side and dully colored underside of its wing.
In some cases the bright coloration of butterflies works to their advantage. Of course, the most famous example of this is the monarch butterfly that is bright orange contrasted with black stripes. In this case, the larval stage feeds on milkweed, which contains some rather toxic materials. These toxins do not harm the caterpillars but are incorporated into their bodies and in turn are passed on to the adult butterflies. Any predator, such as a bird, feeding on either the monarch caterpillar or butterfly, quickly learns not to feed on these distinctly marked insects. In most areas where this species occurs, there is another species called the Viceroy butterfly, which is colored almost exactly the same as the Monarch. The caterpillar of this species does not feed on toxic plants and both the caterpillars and butterflies of this species are totally palatable. Predators rarely eat Viceroys, however, due to their resemblance to the toxic monarch. Such a situation where one harmless species mimics the appearance of a more dangerous species is referred to as Batesian mimicry after the English scientist who first discovered the phenomenon.
The wings of some butterflies lack the scales (clear winged butterflies) and are totally see-through (Figure 15I). I first came across a number of these butterflies when collecting in a rather dense forest in Costa Rica. The lighting in this area was dim and it was very difficult to see the butterflies in flight as they blended in totally with the background (you couldn’t see the wings). This mechanism was very effective as there were hundreds in the area, but I, being a very smart and agile predator (at least smarter than a bird, maybe not as agile), could only find and catch a few.
15I. A clear wing butterfly, lacking the scales that normally give coloration
to the wings.
Image courtesy of Butterfly Farm, San Jose, Costa Rica.
Many moths and butterflies possess eyespots on the hind or underwings (Figures 15J). Obviously the function of these structures is to suddenly appear when the hindwings are exposed and function to startle a potential predator. A number of scientific experiments have been conducted to substantiate the validity of this technique. Predators greatly change their feeding activity when confronted with mere drawings of two circles (simulating eyes) as opposed to squares. When a predator is confronted with the owl butterfly’s underwings, one can only imagine its reaction. It is amazing how nature has mimicked not only the eyes of an owl in this case but the entire face.
Figure 15J. The underside wings of an owl
the perfect face of an owl on the hindwings.
Finally a few butterflies and moths possess long trailing tails on the hindwings (Figure 15K). Although these structures may serve as keel for balance in flight, it is also probable that they function as false targets. Many a bird has ended up with nothing but a pair of broken tails when attempting to catch one of these critters. Once broken off, these structures are not regenerated but one near escape of death is better than none.
Figure 15K. Right. Luna moth. Left. An Indonesian giant silkmoth with long tails.
As discussed throughout this text it is not uncommon for the insect to include other species for defense. Although rare this behavior can extend between insect and other animals of totally different groups, including mammals. Although rare a few species of moths communicate with bats. Some insect-eating bats use echolocation to find their prey. A feeding bat sends out a high frequency beep that bounces off its prey (moths), with the returning beep being detected by the bats large ears. This system works similarly to a destroyer's sonar in detecting a submarine. Some species of moths are capable of detecting the beep of an echolocating bat. If the detected beep is weak, indicating the bat is far away, the moth will fly away as fast as it can in an attempt to avoid the bat. When the beep is strong, indicating that the bat is close, the moth will fly erratically or merely drop to the ground. Although amazing, none of the above is a good example of one species protecting another. However, in at least one species of tiger moth, the beep of an echolocating bat will cause the moth to return a squeak of its own, which is detected by the bat. This tiger moth is foul tasting and any bat that has previously fed on another squeaking tiger moth will associate that sound with the foul taste and break off the hunt.
Unfortunately, a few questionable entrepreneurs have exploited the public by selling pest control devices based on the principle of avoidance displayed by insects and other pests upon hearing certain types of sound. One such device is a small electrical box that is supposed to produce a high frequency sound that drives cockroaches and other insect pests from the home or disrupts their mating biology. Another is a probe that, when placed in the ground, produces a beep that drives gophers from the ground. Unfortunately these devices are totally worthless. I once walked into the backyard or a homeowner who had placed eight of these probes in the ground in attempts to eliminate one gopher. Of course the gopher was still there after 4 weeks of beeping.
Although rare, there have been a few documented cases of one species of insect communicating with another species of insect. There is a species of caterpillar in Costa Rica that possesses glands, which secrete a sweet tasting fluid that readily attracts ants to feed on the liquid. The ants obviously benefit from the relationship by obtaining nutrients from the liquid and the caterpillars benefit by the ants' protection from potential predators. The caterpillar has a ridged area on the front of the thorax which, when rubbed by the back margin of the head, produces a squeaking sound. If a predator attacks the caterpillar, it produces this sound, which alerts any nearby ants to the danger.