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Minnesota State University, Mankato
Minnesota State University, Mankato

Examining Group Behavior on the Fly

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Examining Group Behavior on the Fly


Biology professor Dan Toma inspects a test tube filled with the infamous, 50-plus-yearold line of Drosophila given to him by Dr. Jerry Hirsch upon Hirsch’s retirement from the University of Illinois, Urbana-Champaign. Each generation of fruit flies lives less than two months and is sustained on Toma’s homemade yeast, sugar, corn syrup and gelatin paté.

Is mob mentality genetic? The answer may lie in the fruit fly. While science may not be ready to make claims about a genetic link to mob mentality, Minnesota State Mankato biology professor Dan Toma is conducting research to identify whether certain behaviors in selected lines of Drosophila, fruit !ies, are a collection of individual behaviors or a population-based behavior. How are decisions made within the group? Are the decisions consistent or random? Do the !ies exhibit the same behavior when they are in a group as when they are alone?

A behavioral geneticist, Toma has more than a decade of research experience with Drosophila. His expertise, a 2009 grant from the Faculty Research Committee, and access to relatively famous genetic lines of fruit !ies combined to make the study a reality. Toma received the noteworthy Drosophila lines from Dr. Jerry Hirsch upon Hirsch’s retirement from the University of Illinois, Urbana-Champaign. “Hirsch is a pioneer, really the founder of behavioral genetics,” said Toma. Hirsch began developing the lines of Drosophila more than 50 years ago. In the late 1950s, he began a series of experiments questioning how the genes of an organism contribute to complex behavior in animals. By breeding a population of the fruit !y to walk up (against gravity) and another to walk down (toward gravity), Hirsch established distinct behavioral lines of !ies and was the "rst to scienti"cally prove a genetic basis for behavior.

Toma was one of Hirsch’s last students at the University of Illinois, Urbana-Champaign. At the time Hirsch retired, Toma was conducting post-doctoral work in California. Toma requested and received Hirsch’s !y lines and expanded on Hirsch’s work. “From my own experience giving talks on the research, there were frequent inquiries about how individual !ies in these selected populations behaved,” said Toma. He wondered, given the contribution of research on these selected lines to the understanding of behavior, why had no study at the individual level been done?

“Hirsch’s research was population based. But we want to know what an individual !y does. Undergraduate students are working to determine: Is the population-based phenomena of walking up or down a group-based,phenomena of walking up or down a group-based, social mentality? Is it an emerging property or is it simply a collection of individual behaviors?” said Toma. In other words, do the !ies with the genetic predisposition to walk upward continue to do so when they are alone or do they only walk upward as a member of the group?


Toma and Bradley Cook, biological sciences, received a research grant from $e Institute for Research on Energy and the Environment to study comparative gene expression—speci"cally those responsible for hybrid vigor and invasiveness—among the American, Eurasian, and hybrid cattails.

To understand how complex behavior is produced and controlled in organisms and populations of organisms, Toma explained, one must understand the di#erence in behavior of an individual as opposed to the behavior of the population. Toma and his students run individual !ies through a T-choice, clear plastic maze, one at a time. As the !y moves forward in the maze, it comes to a “T” in the tunnel where it must choose to turn and walk up or walk down. As the !y continues through the maze, it makes a series of these decisions. $e maze is located inside a black plywood box with a light at the exit side of the maze to draw the !ies through. $e exact route of the !y and the time it takes it to complete the maze are recorded.

“Flies are a genetic workhorse. A lot of what we know about our own genetics is drawn from the fruit !y. We can "nd the gene in the !y and then we can look for it in the mouse and human,” said Toma. Hirsch and others have proven the genetic basis for behavior. Now scientists like Dr. Toma can extend existing research, conduct new research, and continue to contribute to our understanding of human behavior. Perhaps someday they will be able to identify a genetic explanation for the power of the adolescent peer group.