When Dora Valdez took a picture of a small, black and white chequered butterfly in her garden, she thought it was just that.
“I saw it and I just thought ‘oh my gosh, that’s just so pretty’ and I’d never seen one before, so I thought I would take a picture of it,” Ms Valdez said.
Displayed as Photo of the Week on the Caymanian Compass website, that picture was to become much more than evidence of Ms Valdez’s skills with a camera.
When Stuart Mailer, field officer for the National Trust of the Cayman Islands, saw the butterfly, he identified it as a species never before been seen in these islands, and hopefully would not become a resident.
Ms Valdez’s photograph was actually the first record of a Papilio demoleus, or Chequered Swallowtail, in the Cayman Islands.
Though this little lepidopteran may seem harmless and even beautiful, it has proven to be a highly adaptable invasive species with the capability of becoming a major threat to citrus crops, native trees and the endemic Cayman Swallowtail.
Taking over one lime tree at a time
The Chequered Swallowtail is not native to the Caribbean, but it has spread across the region with intensity.
“Papilio demoleus arriving in the Cayman Islands is potentially bad news for us, because it is an invasive species from the Old World,” said Ann Stafford, a local butterfly expert.
The Chequered Swallowtail’s original range is Southern Asia and the Middle East where it is a major pest of trees in the Rutaceae family, which includes most citrus plants.
The first recorded sighting of the butterfly in the Caribbean was in the Dominican Republic in 2004.
Since then, it has been sighted in Jamaica, Puerto Rico and, now, Grand Cayman.
“Thus far P. demoleus has not had established populations in the islands with the exception of the Dominican Republic,” said Dr. Jacqueline Miller, associate director of the McGuire Centre for Lepidoptera and Biodiversity in Florida.
Citrus groves in the Dominican Republic are ravaged year-round by these butterflies.
“The larvae feed on citrus, particularly lime and they have so many broods a year that they can become a menace of citrus crops,” Mrs. Stafford said.
According to a study done by Dr. Delano Lewis, assistant research scientist at the McGuire Centre for Lepidoptera and Biodiversity, the number of generations produced by the Chequered Swallowtail in a year increases proportionately with proximity to the equator, where as many as nine generations can be produced per year.
Although grown butterflies may feed on many different plants, butterfly larvae are often only able to feed on one or two plants. The larvae of the Chequered Swallowtail have been known to defoliate entire nurseries of young citrus plants in countries where it has established a population.
“I think a lot depends on the parasitoids and natural enemies already present, as well as practices already in place in areas that grow citrus. They are a threat mainly to smaller trees found in nurseries which can be defoliated,” Dr. Lewis said.While the initial introduction of the species into the Caribbean may have been through the importation of citrus trees, the Chequered Swallowtail is a strong flier and can be swept from island to island by weather systems.
Threat to Cayman
The sighting of the Chequered Swallowtail in Grand Cayman may have been an isolated incident, and certainly anyone who owns a citrus tree will hope so.
There is the possibility, however, that the Chequered Swallowtail will emerge as yet another invasive species to arrive on these shores.
“An invasive species is one which breeds and spreads to the detriment of native species,”
said Mat Cottam, manager of the Terrestrial Ecology Unit at the Department of Environment.
The species that could be threatened by the presence of the Chequered Swallowtail include several endangered trees and the endemic Cayman Swallowtail.
According to Mr. Mailer, the Chequered Swallowtail feeds on trees of the family Rutaceae, as do most species of swallowtail butterflies.
While the most common species of Rutaceae are citrus trees, there are several rare native trees in Cayman that are also a part of this family: The endangered Amyris elemifera, locally known as Candlewood; the critically endangered Zanthoxylum flavum, known as Satinwood or Yellow Sanders; the rare Zanthoxylum coriaceum, known as Shakehand; and another Shakehand, Zanthoxylum species, are all species of Rutaceae.
“This newcomer is not only a threat to farmers and backyard citrus growers, but also it’s an even greater threat to our native trees,” Mr. Mailer said.
The Cayman Swallowtail may also be negatively impacted by the arrival of P. demoleus in Grand Cayman.
The Cayman Swallowtail is an endemic subspecies of Grand Cayman, which means that it is found no where else in the world and has the potential to adapt further.
“In another thousand years it would probably evolve to the point where it’s its own species,” Mr. Mailer said.
While the larvae of the Cayman Swallowtail would originally have only fed on the native species of Rutaceae, deforestation has meant that they too are increasingly having to lay their eggs on citrus trees.
“Its truly native food plants are very rare these days,” Mr. Mailer said. “The satinwood is very, very rare, [and] the candlewood is uncommon.”
The Cayman Swallowtail is not considered a pest species, however. In fact, a Year 6 class at Cayman Prep and High School recently won the 2011 Disney Planet Challenge as a result of their efforts to save the Cayman Swallowtail by planting citrus trees and encouraging community members to do the same.
In addition to competing for food, if the Chequered Swallowtail was to establish a population in Cayman, further harm might come to the Cayman Swallowtail through eradication efforts.
“If you had an eradication programme because people’s lime trees are getting demolished, you could wipe out our native species,” Ms. Stafford said.
Anyone who believes they have encountered a Chequered Swallowtail is encouraged to call either the Department of Agriculture or the Department of Environment.