Anyone who has been on St. John lately will attest to the tremendous number of white butterflies flitting about everywhere. It’s quite a treat to come upon these social insects in huge groups along a trail in the V.I. National Park and delight as they alight from a puddle or bush in a great cloud of small white wings. Our 12/28 issue included full coverage of the butterfly phenomenon we’ve been enjoying on St. John, first from environmental lawyer Gail Karlsson in her Connecting with Nature column and also in Amy Robert’s engaging chat with Eleanor Gibney. Enjoy some beautiful photos by Karlsson and Dr. Caroline Rogers.
By Amy Roberts
St. John Tradewinds
Butterflies are common in the Virgin Islands, especially in November and December, but the butterfly population boom during the last few weeks has not been seen for more than 20 years.
“We always have a fair amount of them after a drought,” said Eleanor Gibney, a horticulturist with extensive knowledge of native plant and insect species. “Many members of the family Lepidoptera, the moths and butterflies, have the ability to suspend development of their larvae until specific conditions occur. The more prolonged a drought, the more buildup you get.”
For those whose knowledge of natural science is a little hazy, Gibney explained that, “The larval phase of all moths and butterflies are caterpillars or worms, most of which eat the leaves of plants.”
Droughts make it hard for them to find food, she said.
“Some local butterflies have larvae that wait specifically for heavy rains after a severe summer drought,” Gibney said. “The last time we saw a notable explosion of butterflies was the fall of 1994, which was an extraordinarily dry year in the spring and summer. Possibly, the current batch of butterflies include larva that have been waiting up to 21 years—this strategy would insure a healthy re-population if a drought wiped out all the current adults and feeding larvae.”
The Virgin Islands, like most islands in the Lesser Antilles, went through a record-breaking drought this past year. The rains in April that traditionally douse carnival celebrants on St. Thomas never materialized. Although Hurricane Season brought rain to other Caribbean islands, the Virgin Islands remained parched.
St. Croix, which relies more on agriculture than the other islands in the territory, was designated as a primary natural disaster area by U.S. Agriculture Department Secretary Tom Vilsack on August 11.
The drought abated in October, and November storms brought 9.53 inches of rain to St. John, exceeding the average for the month by 2.61 inches. However, local residents who anxiously watch the level of their cistern water know that the rain deficit has not been eradicated. The 33.30 inches of accumulated rainfall on the island for 2015 is still 11.22 inches below the average of 44.52 inches.
But the butterflies don’t seem to care.
“It’s like a blizzard of butterflies out there!” said one resident.
The larvae of the most common species, Great Southern White [Ascia monuste], which range in color from white to pale yellow, are chomping down on their favorite local food — plants that are members of the mustard, cleome, and caper families.
And they are dazzling residents and tourists with their antics.
“I had a butterfly fly through my car window and then out the other side,” said Keryn Bryan. “I didn’t know they were so skillful. He was probably thinking, ‘Wow, I flew in and out of a car today!’”
The Great Southern White, which thrives everywhere from Florida to Venezuela, isn’t the only type that is flourishing, explained Gibney
“We are also seeing quite a number of deeper yellow sulphur butterflies, and orange and black gulf fritillaries,” she said.
Butterflies have recently been blamed for eating all the leaves of the flamboyant trees, and Gibney wants to set the record straight.
“The most conspicuous defoliation occurring recently is of our flamboyant trees, leading some to suppose that the clouds of butterflies we’ve been seeing are the adults of inchworm type caterpillars that are often visible going up and down the flamboyant trunks or hanging by threads from their branches,” she said. “Actually the flamboyant worm is the larva of a moth, a not very conspicuous one. The caterpillar arrived in the VI in the 1980s, about a century after the flamboyants were introduced to the region from Madagascar.”
White Christmas: A Blizzard of Butterflies
by Gail Karlsson
St. John Tradewinds
What a joyful holiday season! It has been lovely to go for a walk accompanied by a magical fluttering of yellowish-white butterflies. It is enough to make anyone feel like a Disney princess, or like Bambi exploring a technicolor forest.
In other years there have sometimes been sudden butterfly hatchings, but I have never seen so many, or for so long. It seems that when the heavy November rains broke our six month drought and trees were able to grow new leaves, that in turn created unusually favorable conditions for butterfly eggs to develop into caterpillars that could grow and thrive and produce an abundance of butterflies.
Although there are several similar types of butterflies around, the ones I have been seeing the most are Great Southern Whites. You can tell because they have distinctive turquoise tips on their antennas.
The Great Southern Whites are not special to the Virgin Islands. They are also common throughout the southern United States, South America and the Caribbean. Other Caribbean islands have reported mass hatchings this season as well.
In the Virgin Islands, the Great Southern Whites tend to use the numerous, local limber caper trees as hosts. The females attach clusters of about 20 tiny torpedo-shaped eggs to the leaves of the tree; potentially producing up to 500 eggs each. When conditions are right, the eggs develop into caterpillars with black spots, dark hairs, and yellow stripes running lengthwise along their backs, much smaller than the well-known frangipani caterpillar.
After two or three weeks of feeding on leaves, the caterpillar will transform into a chrysalis with a hard shell, usually hanging inconspicuously on the tree. After a week or so, the chrysalis bursts open and the butterfly emerges. All in all, it is an amazingly complex process.
Butterflies mostly suck nectar from flowers, using a long proboscis that they can extend and insert into the flowers. They are important pollinators for many plants, transferring pollen from one flower to another as they flit about.
The Great Southern Whites also seem to be social drinkers. I have often seen them gathering in groups along on our dirt road, apparently getting together to drink and draw minerals from the wet spots, an activity known as “puddling”
Unfortunately these butterflies have a short life span and will all be gone soon. In the meantime they have brought great joy to people on St. John, and we can hope for another big batch of them agai — if all the eggs these ones lay are able to hatch, and there are enough leaves for the hungry caterpillars to eat, as well as nectar-filled flowers for the next generation of emerging butterflies.