A cluster of photographers were bent over their tripods staring intently into their lenses. Other people stood by gripping binoculars while gazing fixedly in the same direction. They were gathered at the International Butterfly Park south of Mission, and the object of their intense interest was a butterfly that had never been seen before in the United States.
When Sue Sill, Director of the North American Butterfly Association (NABA) Park, recently called to tell me there was a butterfly at the Park which had not been documented north of the Rio Grande I quickly decided to check out the rare One-spotted Prepona.
When an unusual bird or butterfly is discovered it doesn't take long for the word to spread, and when the creature is a first time visitor to the United States it is momentous news among bird and butterfly enthusiasts. After arriving at the NABA Park, I had no trouble finding the rarity as there were a dozen or more people crowded around the insect which appeared oblivious to all the attention.
The large butterfly was perched atop a fence post that apparently had been smeared with a fruit mush concoction. With its rather bland tannish wings folded, the butterfly steadily worked its proboscis or tongue into the mix gleaning sustenance.
Occasionally, the butterfly would part its wings ever so slightly for a tantalizing glimpse of the swath of brilliant blue adorning its topside. Gasps of awe and exclamations of delight would emanate from the onlookers, and then as the butterfly closed its wings all present would plead in unison for another longer look.
Such is the plight of butterfliers, as the creatures they pursue frequently tempt, but do not always display their colorful wares. Those hardy enthusiasts who were willing to devote hours of vigilance were eventually rewarded to varying degrees with displays of colorful wings.
Dave Hanson, a friendly and knowledgeable volunteer at the Park, was on hand to answer onlooker's questions. "This butterfly is called a One-spotted Prepona, and it is a Mexican butterfly that is not even in Northern, Mexico. It is actually in coastal Mexico in the Tampico area and south. As far as we know it has never come to the United States before."
And just in case you were wondering how the One-spotted Prepona got its name, Valley butterfly expert, Gil Quintanilla from Mission has the explanation. "There are many preponas in the Tropics and common names try to utilize a feature that distinguishes one from another. In this case, the One-spotted Prepona "usually" has one hindwing cell spot which can be seen from the butterfly's ventral (closed) position. The prepona seen at the Park seemingly is an exception and does not have an obvious cell spot marking. What it does have is a rounded postmedian line which distinguishes it from other preponas."
The Rio Grande Valley is the nation's number one birding and butterflying destination, with more than 510 species of birds and 308 varieties of butterflies having been documented in the four county area. Birdwatchers have been coming to southernmost Texas for decades, but the Valley is also attracting increasing numbers of butterfly enthusiasts, and the 100 acre International Butterfly Park is a favorite haunt.
The Valley has several distinct habitats from coastal plains to arid chaparral that harbor a variety of native species that are not found farther north, and the thin line of riparian river woodlands, of which the Park is a part, is often the site of rare tropical butterfly wanderings. Since 2003 there have been 16 U.S. records documented in the Valley, and six have been recorded at the NABA International Butterfly Park.
"Some of the rarest butterflies in the United States including this One-spotted Prepona have come here," Hanson said. "We have had several north American butterfly records here in the Park. It is a wonderful place, and we get people from everywhere. We have had people from Australia, from England, all over the world, South Africa, and we have also had people from every state in the United States."
Many butterfliers start out as birders, but gradually become even more infatuated with the colorful winged insects than the feathered avians. Jim Hengeveld, his wife and another couple all form Bloomington, Indiana travel to the Valley every fall to see butterflies.
"We have been coming down for our Thanksgiving break for the last five years now," Hengeveld said. "The Rio Grande Valley is one of the prime birding locations in the country, and that is why we were coming down. Then we got into butterflies, and it sort of hooked us, and now we come down primarily for butterflies."
In addition to seeing the One-spotted Prepona, the visitors from Indiana were excited to encounter another butterfly near Zapata, the Guatemalan Leafwing, that was also a U.S. first. "The chance to see butterflies that have never been documented in the United States is a real thrill," Hengeveld said. "That's what makes it so exciting. Two first U.S. records in one day are amazing, and you almost never have that opportunity with birds anymore."
One reason that the Valley butterfly tally keeps expanding, with never before documented species being identified, is that there are simply more knowledgeable butterfly enthusiasts in the field, whereas just a few years ago there were not many. This phenomenon is known as the "Patagonia Picnic Table Effect."
Years ago, birders frequented a public picnic table in the little town of Patagonia, Arizona and saw a rare bird that had wandered up from Mexico. Other birders heard about this, and they stopped too. Before long the list of rarities had multiplied as the number of watchers increased, and so what is known as the "Patagonia Picnic Table Effect" has entered the lexicon of birders and butterfliers.
While first time records are thrilling, many come to the Park to see alluring Valley specialties like the Mexican Bluewing, Malachite, Red-bordered Pixie and Two- barred Flasher that are not found anywhere else in the U.S. "About 180 species and counting have been seen here at this park since we opened in 2003," said Sill.
Texas leads the nation in number of butterfly species with more than 400 occurring state wide. "There are more than 300 species that have been seen in the Valley, and that is really close to the same number of species that they find in the whole state of Arizona and New Mexico which are the only two states that have even close to as many butterflies as Texas," said Sill.
"We have a great time every time we come down to the Valley, and that's why we keep coming back," Hengeveld said. "It's wonderful. The birds and the butterflies bring us."
The Valley tally of rarities is growing, and while the one-spotted prepona has vanished there is no telling what new butterfly will show up next. And with increasing numbers of dedicated butterfly watchers in the field, the chances are good that the next U.S. record will be spotted soon.
If you are interested in learning more about South Texas butterflies, you may want to visit the NABA International Butterfly Park south of Mission near Bentsen State Park. The number to call is 583-9009. A great website to learn about Valley butterflies is www.naba.org/chapters/nabast where you can find checklists and photos of virtually every butterfly documented in the Valley and the "hotspots" where they can be seen. The Park is also seeking a new executive director to supervise continued improvements.
Copyright 2007 Richard Moore