|The long history of the rainforest has enabled countless butterflies, moths, ants, termites, wasps, bees, and other tropical insects to evolve in astounding profusion. Ant species alone number in the many thousands. Corcovado National Park boasts at least 220 species of breeding butterflies, plus others that simply pass through. And there are so many species of beetles and grasshoppers that no one knows the true numbers. Many, many thousands of insect species still await identification.
The most brilliantly painted insects are the butterflies and moths, some quite tiny and obscure, others true giants of the insect kingdom, dazzlingly crowned in gold and jewel-like colors. In Guanacaste, hundreds of species of bees, moth larvae, and tiger beetles make an appearance in the early dry season. When the first rains come, lightbulbs are often deluged with adult moths, beetles, and other insects newly emerged from their pupae. That's the time, too, that many species of butterfly migrate from the deciduous lowland forests to highland sites.
Many insect species are too small to see. The hummingbird flower mite, for example, barely half a millimeter long, is so small it can hitch rides from flower to flower inside the nostrils of hummingbirds. Other insects you may detect by their sound. Male crickets, for example, produce a very loud noise by rubbing together the overlapping edges of their wing cases.
Many exotic-looking species are immediately recognized. The giant Guanacaste stick insect is easily spotted at night on low shrubs. The three-inch rhinoceros beetle has an unmistakable long, upward-curving horn on its head. And the number of spiders ornamented with showy colors is remarkable. Some even double themselves up at the base of leaf stalks, so as to resemble flower buds, and thus deceive the insects on which they prey.
Of course, a host of unfriendly bugs also exist in great numbers: chiggers, wasps and bees (including aggressive African bees), ticks, mosquitoes, fire ants, and the famous "no-see-ums" all can inflict irritating bites on humans.
Ants are the most abundant insects (one hectare of rainforest contains an average of nine million ants). Though related to bees and wasps, like butterflies they pass through four life stages: egg, larva, pupae, and adult. They are entirely social creatures, each ant within a colony entirely dependent upon its siblings so that the colony (which may contain many million individuals) acts as a single organism. They are also almost entirely blind and rely for communication upon the chemicals--pheromones--that they release to alert each other to danger and food sources.
Each colony is dependent upon the queen ant, whose sole task is to keep producing eggs (thus, most colonies die when the queen, which can live up to 20 years, dies). Only the queen, who may boast a thousand times the body weight of a minor worker, is fertile. Once a year, usually at the beginning of rainy season (around May and June), the queen produces a unique brood of about 50,000 eggs; the approximately one-fifth that are fertilized will become new queens, and the others will become males. The entire colony doubles its efforts to care for and feed the large larva. Upon maturity, males and queens develop wings and upon a particular weather cue (usually following a large rainstorm), the progeny from many colonies emerge in synchronicity and swarm in a massive orgy in which queens are mated many times, collecting sperm to be stored and used throughout their lifetime. Males exist only to fertilize the queen and then die.
The queens then rip off their wings and disperse to start their own individual colonies by burrowing into the soil, laying eggs (see special topic, The Underworld of the Leafcutter Ant). Only about one percent of queens successfully start new colonies. If the colony survives its first year, it may grow large enough to produce soldiers with which to defend it; after three years it will grow large enough to produce new queens and males, and its continuation might be assured.
The most terrifying ants of all are the army ants, which march through the forest with the sole intent of turning small creatures into skeletons in a few minutes. They produce a faint hissing sound and distinct ant-army odor. They're like a wolf pack, but with tens of thousands of miniature beasts of prey that merge and unite to form one great living creature.
Hollywood images of mammals and even humans fleeing madly before them are mostly imagination run wild. In truth, while the ants advance across the forest floor driving small creatures in front of them, humans and other large creatures can simply step aside and watch the column pass by--this can take several hours. Even when the ants raid human habitations, people can simply clear out with their food stock while the ants clean out the cockroaches and other vermin as thoroughly as any exterminator might.
The army ants' jaws are so powerful that indigenous people have traditionally used them to suture wounds: the tenacious insect is held over a wound and its body squeezed so that its jaws instinctively clamp shut, drawing the flesh back together. The body is then pinched off.
Larvae carried by workers produce pheromones which stimulate the army to keep moving. When the larvae begin to pupate and no longer exude chemical messages, the ants bivouac in a vast ball in a hollow. They actually cling to one another and make a nest of their bodies, complete with passageways and chambers where the eggs are deposited.
Once the queen lays her eggs and these hatch as larvae, a new generation of workers and soldiers emerges from the stored pupae. The larvae begin to secrete their characteristic pheromone, and the army is again stimulated to march off and terrorize the bush.
| THE UNDERWORLD OF THE LEAFCUTTER ANT |
|Image © Bob Race|
There's something endearing about the leaf-cutting ant (Atta cephalotes), a mushroom-farming insect found in lowland forests throughout Costa Rica, carrying upright in its jaws a circular green shard scissored from the leaves of a plant. At some stage in your travels you're bound to come across an endless troop of "media" workers hauling their cargo along jungle pathways as immaculately cleaned of debris as any swept doorstep.
The nests are built below ground, sometimes extending over an area of 200 square meters, with galleries to a depth of six meters. The largest nests provide homes for single colonies of up to five million insects. Trails span out from the nests, often for 100 meters or more. The worker ants set off from their nests day and night in long columns to demolish trees, removing every shoot, leaf, and stem section by tiny section and transporting them back to their underground chambers (about 15 percent of total leaf harvesting in Costa Rica is the work of leafcutter ants; they are a perpetual pest to commercial crop farmers, who often resort to igniting the nests with petroleum, usually to no avail).
They don't eat this material. Instead, they chew it up to form a compost on which they cultivate a nutritional breadlike fungus whose tiny white fruiting bodies provide them with food. So evolved has this symbiosis become that the fungus has lost its reproductive ability (it no longer produces sexual spores) and relies exclusively on the ants for propagation. When a new queen leaves her parent colony, she carries a piece of fungus with her with which to start a new garden.
The species has evolved different physical castes, each specializing in its own social tasks. At the apex of the leafcutter colony is the queen, which may be five centimeters long. The cutting and carrying are performed by intermediate-size workers ("medias"), guarded by ferocious-looking "majors," or soldier ants, about two centimeters long and with disproportionately large heads and jaws that they use to protect the workers -- usually fighting to the death -- from even the largest marauder. They also work to keep the trails clear. Most of the workers are tiny minors ("minimas"), which tend the nest and mulch it to feed the fungus gardens. Even small "minimas" ride atop the leaves carried by their larger siblings to guard against parasitic phorid flies that attempt to lay their eggs on the leaves so that the eggs may be taken underground, where they will hatch and feed on the ant larvae.
With nearly 1,000 identified species (approximately 10 percent of the world total), Costa Rica is a lepidopterist's paradise. You can barely stand still for one minute without checking off a dozen dazzling species: metallic gold riondinidae; delicate black-winged heliconius splashed with bright red and yellow; orange-striped paracaidas; and the deep neon-blue flash of morphos fluttering and diving in a ballet of subaqueous color. The marvelously intricate wing patterns are statements of identity, so that individuals may recognize those with whom mating may be fertile.
Not all this elaboration has a solely sexual connotation. Some butterflies are ornately colored to keep predators at bay. The bright white stripes against black on the zebra butterfly (like other members of the Heliconid family), for example, tell birds that the butterfly tastes acrid. There are even perfectly tasty butterfly species that mimic the Heliconid's colors, tricking predators to disdain them. Others use their colors as camouflage so that at rest they blend in with the green or brown leaves or look like the scaly bark of a tree. Among the most intriguing, however, are the owl-eye butterflies, with their 13-cm wingspans and startling eye spots. The blue-gray Caligo memnon, the cream owl butterfly, is the most spectacular of the owl-eyes: the undersides of its wings are mottled to look like feathers and two large yellow-and-black "eyes" on the hind wing, which it displays when disturbed, give it an uncanny owl's face appearance.
The best time to see butterflies is in the morning, when most species are active. A few are active at dawn and dusk, and one species is even active by night. In general, butterfly populations are most dense in June and July, corresponding with the onset of the rainy season on the Pacific side. Butterfly migrations are also common. Like birds, higher-elevation species migrate up and down the mountains with changes in local weather. The most amazing migration--unsurpassed by any other insect in the neotropics--is that of the kitelike uranidae (this black and iridescent green species is actually a moth that mimics the swallowtail butterfly), in which millions of individuals pass through Costa Rica heading south from Honduras to Colombia.
| MORPHO BUTTERFLIES |
Undoubtedly the Narcissus of the Costa Rican butterfly kingdom is the famous blue morpho, one of the most beautiful butterflies in the world. There are about 50 species of morphos, all in Central and South America, where they are called celeste común. The males of most species are bright neon blue, with iridescent wings that flash like mirrors in the sun. Sadly, this magnificent oversized butterfly--it grows to 13-20 cm--is not as common as it once was, thanks to habitat destruction.
"It used to be a backyard species; now it is found only in reserves," says Maria Sabido, cofounder of the Butterfly Farm, in La Guácima de Alajuela. Still, you can't miss them when they're around and active--particularly in November, when they are extremely common along riverbeds and other moist habitats.
The morpho is a modest, nondescript brown when sitting quietly with wings closed. But when a predator gets too close, it flies off, startling its foe with a flash of its beautiful electric blue wings. (Not that they are always successful. Biologist David Janzen reports that piles of morpho wings are often found under the perches of jacamars and large flycatchers, which are partial to the morpho.)
The subspecies differ in color: in the Atlantic lowlands, the morpho is almost completely iridescent blue; one population in the Meseta Central is almost completely brown, with only a faint hint of electric blue. One species, commonly seen gliding about in the forest canopy, is red on the underside and gray on top.
Showmen have always used mirrors to produce glitter and illusion. The morpho is no exception. Look through a morpho butterfly's wing toward a strong light and you will see only brown. This is because the scales are brown. The fiery blue is produced by structure, not by pigment (one consequence is that the color will never fade). Tiny scales on the upper side of the wing are laid in rows that overlap much like roof shingles. These scales are ridged with minute layers that, together with the air spaces between them, refract and reflect light beams, absorbing all the colors except blue. The Atlantic species have additional glassy scales on top of the others to reflect even more light and give the wings a paler, more opalescent quality.
More than a dozen "butterfly farms" nationwide let you walk inside netted butterfly gardens; see regional chapters. Selva Verde Lodge, tel. 766-6800, fax 766-6011, email: email@example.com, offers butterfly-study workshops (1-9 days).