© Photo by Amanda Baker 2001

It’s late afternoon. I’m walking along one of the shady forest trails of Mount Sage National Park. In what seems like only seconds, the sky begins to darken. A cloud passes overhead so close I can feel the mist. It is as if day quickly turned to night, and it was time to return to my car and drive home. However, I was not the only creature reacting to this sudden twilight. A chorus of Whistling frogs, locally called Bo Peeps, erupted into full song from the nearby foliage. Insects and birds chimed in to welcome the darkness and announce their presence.
But, it was not the sounds that captured my attention. Rather, I was drawn to the black and yellow butterfly that fluttered mere inches from my face. It flew across the trail and down the path, following the border of shrubbery. I kept pace as it visited flowers and leaves in a seemingly erratic and random flight. Suddenly, it vanished. I gazed toward the bushes where only a moment before its bright conspicuous markings made it easy to follow. Then, from a different direction, another black and yellow butterfly flew into the same bush and also disappeared. Within a few moments a third and then a fourth butterfly also vanished into the bushes.

My curiosity aroused, I edged closer for a better look. I strained my eyes looking for the distinctive black and yellow markings. All I could see was the tropical forest greenery and a bare branch with what appeared to be dried leaves at the tips. By accident, I bumped the branch and the “leaves” exploded into a dozen black and yellow butterflies fluttering in all directions. Startled, I stepped back to observe this strange event. Rather than flying off into the forest or disappearing down the path, these butterflies remained in the area. Some flew through the shrubbery as if searching for a flowery feast. Occasional pairs engaged in what looked like the butterfly equivalent of courtship. Then slowly, one by one, they all returned to the same dead branch. The sudden transformation from bright black and yellow flying butterfly to the drab camouflage of their folded wings was remarkable. I was witness to one of the seldom seen spectacles of the tropical forest; the nightly gathering of the Zebra Butterfly to a communal roost.
Such nightly roosts are but one of the fascinating tales surrounding this remarkable insect. The Zebra Butterfly, or Heliconius charitonius as scientists more properly know it, belongs to a tropical family called Heliconiidae. Neotropical in origin, this group of butterflies exhibits its greatest species diversity on the mainland of Central and South America. Although relatively few species have invaded the islands of theWest Indies, members of this group share a number of interesting characteristics. All have long narrow wings quite different from their temperate cousins. They appear delicate and fragile as they flutter through the tropical landscape. But, it is the striking colour pattern that is most distinctive. All members of this family are brightly coloured and conspicuously marked. Some species from the mainland display breathtaking bright colours. But, why should this be so? Why would such aslow flying, fragile looking insect advertise itself to potential predators? Could it be that this little animal has a proverbial “trick up its sleeve”? Indeed it does.

In the insect world, bright conspicuous colours or patterns are often a sign of danger. An insect that so boldly advertises its presence usually has some effective means of defense.
Scientists call this “Warning Colouration”. Usually it means the animal has a potent sting or some special chemical defense. So it is with the Zebra Butterfly. Members of this group contain chemicals that are distasteful to predators, especially birds. These substances, called alkaloids, are consumed by the caterpillars as they feed on their only food, the Passion Vine, and retained as the caterpillar metamorphoses into the beautiful adult butterfly. Proof of this can be found by examining the adult butterfly. Many exhibit injuries such as broken body parts or damaged wings. Sometimes the outline of a bird beak is clearly visible on the wing. Avoiding noxious insects is not instinctive in birds. They learn it through trial and error and some Zebra Butterflies are living proof of this learning curve.

Butterfly experts, Lepidopterists as we call them, are fascinated by the entire family of Heliconiid butterflies. They have discovered that most butterfly species have a life span measured in days or weeks, while Zebra Butterflies may live for years, giving them an opportunity to learn the lay of the land not possible for their shorter lived relatives. These advantages may translate to better survival techniques for this group. Although the Zebra Butterfly is widespread from Florida to Peru, our own variety, a subspecies, is restricted to those islands between Montserrat and Puerto Rico. Originally described in 1767 from a specimen labeled Virgin Islands, it is one of only three species of Heliconiid Butterflies found in the B.V.I.
So the next time you wander down a shady trail in the late afternoon, keep an eye out for the distinctive yellow and black stripes of the Zeba Butterfly. When you see one, follow it quietly and it will lead you to a roost. The you too can marvel at a spectacle that is an everyday occurance in the Caribbean Tropical Forest.

Courtesy of BVI Welcome Tourist Guide, Vol. 30, No. 5 - August / September 2001.