Sexual attraction between humans is a complicated dance. It involves style, flair and a certain suave to make the movement complete. And adding even more intricacies to the already convoluted process — every person enjoys their own dance style.

Some live for the flighty quick step, chasing after their partners in emotional bursts. Others enjoy the slow lyrical jazz, full of sensuality. And even more want the rigid tango, trapped in a whirlwind of passion. It often seems miraculous to find two people whose timing, speed and style match in elegant movement.

Luckily for moths, and many other species, reproduction isn’t nearly as difficult of a selection process. Rather than creating a perilous system including everything from movement to appearance to intelligence, moths rely simply on chemical signals called pheromones. But a moth’s current genetic code has taken millions of years of evolution to reach where it is today — and the details of how pheromones evolved from one species into thousands has puzzled scientists for decades.

But an inter-disciplinary study on campus delved into this complex world of moth reproductive attraction. A group of professors used genetics and entomology to investigate moth pheromones.

“Pheromones as a group is the communication within the species,” Astrid Groot, a professor of entomology, said. “Allomones is the communication between species.”

Pheromones are most often recognized as sexual, and although they do refer to other communications between specimens, arguably the most important and at the center of this study, are sexual pheromones.

To explain the complexity of the moth pheromone situation, Fred Gould, a professor of entomology, contrasted with the evolution of changing colors of Melanic Moths.

“[Melanic moths] fly at night, but during the day they rest on the bark of trees. And years ago the bark of trees in England was a light silvery color so the moths evolved in color to blend in perfectly with the tree so birds couldn’t find them,” Gould said. “And then came industrialization, so all the soot came from the factories covering everything in black, and this moth would land on the tree and stick out like a sore thumb. And so the birds would feed on it. Well, those moths ended up having a genetic mutation making them darker in color, making it harder for birds to find them, and then the entire population became darker.”

This example follows natural selection by a species morphing for survival. But by changing their pheromones female moths can actually hinder their attractiveness for reproduction, creating what Gould refers to as an “evolutionary valley.”

“In changing the pheromone blend both the female and male have to evolve, and the first to do so is at a disadvantage,” Gould said. “We call this an evolutionary valley, where on a peak they communicate and then they have to go through the valley to reach the other peak with a new pheromone and a new response.”

Gould relates this as an exercise in evolution versus intelligent design because the pathway to a complex result is very different.

“It’s this idea that you have irreducible complexity — that you look at things that are very complicated like your eye — and your quick response may be that it’s not evolutionary because it’s too complex,” Gould said. “It’s not like the Melanic moths. When studying the evolution of complex traits researchers must look at each system very carefully to find the key factors that enable evolution.”

The study by Groot, Gould and Coby Schal, also an entomology professor, looked closely for the key factors that could explain evolution of these moth pheromones using two species: Heliothis subflexa and Heliothis virescens.

The moths are kept in various stages in a Method Road Lab.

The tiny larva feed in tiny plastic cups in a room labeled “baby room” on a sign with pastel letters and pictures of rocking horses. Down the hall is the much racier “mating room” designated by pictures of black lingerie and alcoholic beverages — not that martinis would change their situation of pheromones and plastic containers.

Inside the lab, H. subflexa females are backcrossed to breed females lacking three acetates identified for attracting mates.

“In moths the sexual attractant chemical blends are most important because they are night flying,” Groot said. “They [essentially] have no ears and very limited hearing but they have antennas very adapted to smell. Only one [pheromone] molecule is needed for attraction.”

The results of negating three important compounds in H. subflexa females surprised everyone, because not only were they less attractive to their own males, but male H. virescens became attracted to them.

This cross-species attraction can be a very large problem because it creates sterile males and females with problems laying eggs as well as other issues. And since H. subflexa females usually have three rounds of offspring, mating with the wrong species can reduce fertile young by 23 percent, according to Groot

The females found a way to adapt, altering their pheromones in a way that would make them very unattractive to other species — even though this also results in being less attractive to their own species. And once the females have changed, a mutation in the males unites the species together once again, Groot explained.

“In one sense we can look at this as a story about pheromones,” Gould said. “But in another sense it’s much deeper about how complicated behaviors evolve.”