PANAMA'S WINGED JEWELS
The Panama Canal Review. . . Spring 1973
A benign climate, rich and
varied vegetation and great diversity of terrain have combined to produce an extraordinary
abundance of butterfly life on the Isthmus.
"Sparkling sapphires studding the dark green forest canopy" - Thus an enthralled newcomer to the Isthmus described the dazzling spectacle of blue 'Morpho' butterflies viewed from a low-flying aircraft. Logically known as "Royal Blues," these huge butterflies with wingspans up to 6 inches are unique to the American tropics, and rank among the most beautiful creatures to be found in nature.
At least five distinct species of 'Morpho' make their home in the forests of Panama. Males are frequent sights, flaunting their brilliant color over the forest canopy and along trails and rivers. Greatly prized by collectors are their scarce and more sober mates, which unobtrusively wend their way through the foliage tending to egg laying chores.
In Brazil, 'Morphos' are raised commercially for the purpose of making showy trays out of their wings. The colors never fade, as they are produced in a purely physical way by diffraction of light in specialized scales in the wings, rather than by pigmentation.
Splendid as are the 'Morphos,' they are rivaled on the Isthmus by many hundreds of other species, attired in a veritable kaleidoscope of colors and patterns.
Panama's benign climate, rich and varied vegetation, and great diversity ofter rain have combined to produce an extraordinary abundance of butterfly life. Well over 1,100 species are known, and probably more await discovery. Quite an incredible number when one considers that less than 700 species are known in the entire United States, a country with an area more than 125 times larger.
DUE TO SCALES
Together with the moths, butterflies are members of the group of insects known as Lepidoptera. The term is derived from the Greek words lepis (scale) and pteron (wing) and indicates that these insects are distinguished by the possession of scales on their wings. All the varied color effects of a butterfly's wings are due to these scales.
Nature does not really distinguish butterflies from moths. Various structural differences can be cited to separate the two but exceptional cases are all too frequent. It suffices to say that most butterflies are brightly colored and fly in the bright sunlight, whereas most moths are dull and nocturnal.
As is well known, butterflies represent the adult phase of a creature that has progressed through the stages of egg, caterpillar, and pupa before reaching its final winged form. The caterpillars of butterflies are
exceedingly voracious and devote virtually every waking moment to gorging themselves on the leaves of their specialized food plants. They store up so much energy that feeding for the winged adult is hardly necessary -more
of a snack than a meal. Fortunately for the human race, the caterpillars of relatively few species are addicted to plants of agricultural or economic importance, and, of these, even fewer are numerous enough to be labeled "pests."
Most butterflies are closely associated with a particular species of plant, on which their caterpillars feed to the exclusion of all others. Sir Winston Churchill became aware of this when he endeavored to determine the particular plants that it would be necessary to grow in his garden to attract butterflies. to his dismay of his gardener, it turned out that several showy species could be enticed only by beds of stinging nettles! In the tropical forest, individual specimens of a given plant often tend to be widely separated from each other, and consequently, the butterflies associated with these plants may seldom be seen, even by experienced collectors. In addition, the character of the forest changes markedly as one ascends mountains or travels to areas of different geological
characteristics. So, it is not surprising that many of the butterfly species found on the Isthmus, say, at an elevation of 2,500 feet at El Valle, are quite different from those in the Madden Forest Preserve.
BOCAS DEL TORO
Considering these factors, it is doubtful that one man could ever succeed in collecting all the species of even a limited area like the Canal Zone; and thus, the never ending search for rarities is one of the fascinations
of making a collection. A number of the species known from Panama are so scarce or localized or elusive that only one or two specimens have ever been captured. Remote forested areas of the provinces of Bocas del Toro
and Darien are virtually unexplored for insects, and hold the lure of unknown species.
In the tropics, butterflies have rather brief lives, most individuals probably not surviving a month. But a few hardy types of the temperate zone can endure almost a full year, hibernating through the hostile winter months.
Flowers are visited by many butterflies insert of nectar, yet some disdain flowers altogether, preferring oozing sap or the juice of fermenting fruit. Collectors capitalize on this predilection by preparing such recipes as
rotting bananas, molasses, and brown sugar, spiked with a dash of rum. The concoction is left to ferment for several days, and then placed in specially designed traps. In this way certain magnificent and unusual denizens of the forest canopy can be lured to ground level and captured easily.
We are apt to regard butterflies as delicate ornaments aimlessly flitting about the countryside. Indeed, one ardent naturalist of the Victorian era declared that the presence of butterflies provided clear proof of the existence of God. What possible explanation could there be for such resplendent, fragile, useless creatures, other than they were expressly created by the Almighty simply to gladden the eye of mankind. Unfortunately for such romantic notions, the butterfly is far from a carefree creature. At all stages of his life, he is beset by a multitude of perils, to which the majority of his brethren quickly succumb.
The winged adult is entrusted with two vital missions -reproduction and dispersal. Males often stake out territories which they defend belligerently, viciously flying at potential rivals or other insects which invade their domain. Should a female appear, she is quickly courted, and after a short display of feminine coyness, is usually won over.
Far from being mere trappings, the resplendent colors and striking patterns of a butterfly's wings are the product of millions of years of evolution through the process of natural selection, and play a vital role in his survival. For example, eyespots are a conspicuous feature of the wings of many butterflies. In the "owl butterflies" they are large and conspicuous, and presumably serve to startle potential predators. The drab brown butterflies known as Satyrs, which fly amid the gloom of the forest floor, are equipped with a series of eyespots on the edges of the wings. There is some evidence that these serve as a kind of target for predators. A potential villain scoring a bull's-eye would have nothing but a chunk of indigestible wing to show for his marksmanship.
COPIES OF DRY LEAVES
Many species of butterflies are colored so as to blend in with their surroundings when at rest. Most spectacular of these are a group of butterflies that become faithful copies of dry leaves when they alight on a twig. One kind in particular has so perfected the disguise that it not only appears identical to a dead leaf complete with stem and veins, but also has several small transparent areas in the forewing, suggesting grubholes. The likeness to the real thing is so uncanny that it seems almost incredible that it could have been brought about by natural processes. Even the most dispassionate scientist must be given cause for wonder.
Another remarkable protective effect is attained by certain small butterflies known as "hairstreaks," because of the fine hairlike lines on the undersides of their wings, At the lower end of the under surface of each hindwing is an eyespot together with a projecting pair of thin filaments, suggesting antennae. In this way a realistic false head effect is produced when the insect is at rest. Some hairstreaks have, in addition, dark stripings that pass uninterrupted from the upper wings to the lower wings, and focus one's attention on the false head area. As soon as the butterfly alights, it moves its hindwings back and forth, causing the dummy antennae to twitch provocatively. Thus a potential predator is prone to lunge at the sham head, and the butterfly makes a hasty exit with the loss of only a portion of its wing, and perhaps a little dignity.
In some butterflies, a bold striking pattern and slow lazy flight are used to advertise the fact that their bodies contain noxious substances and that they would make for a decidedly unsavory gastronomic experience for a predator. Benefiting by bitter experience, birds, for example, come to recognize particular patterns as a sort of warning signal, and give their owners wide berth. With admirable economy, distasteful butterflies tend to standardize into a few distinctive patterns -in doing so, they gain the advantage that the bird's learning process is simplified, and so, fewer of their number are lost. Even the birds benefit, for they then have less unpleasant experiences. All gain, except the befuddled lepidopterist, who finds himself confronted by a multitude of butterflies which all look very much the same, but in reality are a composition of many distinct species. Butterflies which have adopted a common warning pattern are said to from a "mimicry club," and their members are conspicuous sights in the forests of the Isthmus.
The mimicry phenomenon is extremely complex and fascinating. For example, a few perfectly savory species of butterflies have succeeded through the process of natural selection in adopting the warning pattern of the distasteful butterflies of a mimicry club. They have, so to speak, crashed the party. the birds thus avoid them, assuming they are noxious. Paradoxically, these imposters must be rare, otherwise the predators would not learn to associate their particular pattern with distastefulness.
DISGUISES AND MIMICRY
The butterfly is thus a hunted creature that survives like the master spy -by disguises and intrigues and mimicry. But the butterfly can go the spy one better; he sometimes is invisible. Deep in the shade of the forests are found a number of butterflies which have foregone color almost completely, to the point where their wings are largely transparent. Flitting ghostlike through the dappled light and shade they are almost impossible to follow in flight.
It is fascinating to note that in transparent species of different families, nature has used different devices to achieve the common goal of transparency. In the butterflies of one family, the scales are modified in shape, being reduced to fine hairs; in another, the scales retain normal shape, but are greatly reduced in size; in yet another, the scales are set up on edge, so that light passes between them. These facts supply the theorist of evolution with a fine example of how a single effect, transparency, can be brought about by a wide variety of chance genetic mutations and the process of natural selections.
SUBJECTS FOR RESEARCH
For the geneticist, then, butterflies are excellent subjects for research, and the tropics an ideal outdoor laboratory. To the nonprofessional enthusiast as well, the living insect soon becomes even more intriguing than the dried cabinet specimen. Consider, for example the great migrating hordes of black and green "butterflies" that suddenly appear in Panama from time to time. Resembling butterflies both in appearance and behavior, certain structural peculiarities indicate that they should be classed with the moths, in the genus 'Urania." At times, during the most recent large movement, in August and September of 1969, dozens would pass by a given point in a few moments. All were traveling strongly and purposefully in the same direction as if with some single minded intent to reach a definite destination.
Why do they migrate? Where are they headed? Are they, like lemmings, fated to perish without ever reaching a final destination?
Recent research by Dr. Neal Smith of the Smithsonian Tropical Research Institute has shed some light on questions such as these, but also poses even more. His documented records indicate that eastward movements involve a great many more individuals and occur at a different season of the year from westward ones. Surprisingly, some flights are accompanied by reproductive activity, and others are not. In the first case, an advantage could certainly accrue to the species by disseminating its eggs over a wide territory during migration. But what is gained by migrating after the eggs have been laid?
Clearly, we still have much to learn about the behavior of the migrating 'Urania' moths, but even if man succeeds in unlocking all their secrets, a myriad other mysteries will ensure that the Lepidoptera will remain ever alluring and fascinating.
October 2, 1998
Photo Credit (Background): Gregg Pasternack