University Wire

By Laila Rihawi

Forty-eight female phorid flies, each smaller than the size of a pinhead, hover over a colony of red imported fire ants. One fly lingers above a few ants that march across a test tube filled with sugar water. She floats in the air for just another second, selecting the individual in which to lay her egg. Then, so quickly it almost cannot be seen, she dives at the ant of her choice, injects her egg into it and flies away to find another victim.

This all takes place in an “attack arena” lab room in the University of Texas Brackenridge Field Laboratory. And it's all being filmed by National Geographic Explorer for a documentary to be aired in late spring 2007.

The documentary is a natural history film about the red imported fire ant (RIFA), Solenopsis invicta, which arrived in Texas more than seven decades ago from Brazil and Argentina. Since then, the RIFA has spread across the Southeast United States and even westward into Arizona and California.

A key player in the documentary is Lawrence Gilbert, a professor of integrative biology at the university who is doing research on the red imported fire ant and how to control the species in the United States. RIFA pose a threat to wildlife in the South, including native fire ants. According to Gilbert's Web site, RIFA can also kill quail chicks, other birds, small mammals and reptiles. They are also attracted to electrical devices such as circuit breakers and can cause short circuits and fires.

“The problem with these ants is that there is no natural predator to keep them in check here in the U.S., and therefore they have an advantage over the native fire ants,” said Christiane Krejs, program coordinator for the integrative biology section of the College of Natural Sciences.

Gilbert believes that these ants may be controlled by importing a natural predator: Psuedacteon, commonly known as the phorid fly, which keep fire ant populations in South America in check.

When the phorid fly attacks the ant, the injection itself is quick -- it appears as if the fly merely flew towards the ant and away without touching it. After the egg is injected, the ant twitches with shock -- paralyzed for a second -- and then staggers away.

According to Gilbert's Web site, the injected egg develops in the ant's thorax, killing the ant in about 10 days. After that, the larva moves into the ant's head. The head falls off and the larva eventually pupates in the hard chitin shell that once housed the ant's jaw muscles and brain. Adult flies develop after about 45 days. Their adult life is only two to three days, but they may lay eggs in many ants during that time.

When the ants sense phorid flies in their presence, they scurry about to hide, or pile on top of one another, or position their bodies in various postures to avoid being attacked. Flies disrupt the foraging process and the colony itself. As a result, the ants have to put energy into protecting themselves instead of going about their routines.

Indirectly, the phorid flies serve as a sort of bio-police force for the environment. They balance the playing field between RIFA and the fire ants native to Texas, allowing fair competition for territory and resources.

Gilbert told National Geographic News in June 2004 that the phorid flies that prey on ants have a high degree of “specificity” -- meaning they attack only one type of ant. Gilbert said flies that attack the Solenopsis geminata, also known as the common fire ant, in the United States are dwindling as their population of host ants dwindles.

Gilbert's Web site says the fact that native Texan phorid flies have not begun to attack the imported fire ants is “strong evidence of how extremely host-specific these flies are.”

However, the site also says that Texans shouldn't expect phorid flies to provide a solution to the RIFA problem overnight. In fact, the best we can hope for is elimination of the fire ants' “pest status.”

‘An Alien Invasion’

Jeff Morales, staff producer of “Natural History” at National Geographic Explorer, said that filming took place mostly in June and the final touches are being made right now. One challenge of filming, he said, is getting the animal to feel comfortable and do what it does normally.

“Focusing on the high-speed footage to film the fly attack was the most difficult,” said Morales, who has worked with National Geographic and the BBC. “It was tough positioning me to get something that takes place in a split second.”

Morales also produced National Geographic's “Hornets from Hell,” which he filmed in Japan about the giant hornet. His work with that film earned him three Emmy nominations.

“The phorid fly attacks are like something out of a science fiction movie,” he said.

“It's like an alien invasion,” Morales said.  “With the flies hovering around and attacking -- it can be inspirational to the movies.”

Morales' partner for the not-yet-named documentary is Alastair MacEwen, a freelance cameraman and biologist. MacEwen filmed all the close-up work in the documentary.

Some of the footage MacEwen captured for this film shows the damage done by fire ants. One time-lapse clip shows the ants tearing apart a dead earthworm. After 12 hours, not a speck of worm was left by the ants. It took about the same amount of time for the ants to dismantle a dead cricket. He said he might expose a dead quail chick to the ants.

“Game bird chicks are at a high risk,” he said. “Breeders that have them are frustrated because these ants get under the nests and the chicks get attacked when they hatch. They're helpless. Ants also attack the sick and injured animals.”

More filming will take place down in Beeville, Texas about three hours south of Austin. “Two ranchers heard about the fire ant project, so they dug up fire ant colonies from their land to get them to the Brackenridge Field Lab and have them exposed to the phorid flies,” Krejs said.

“Working with the ranchers has helped to personalize the story being told in this film,” Morales said.