Research Roundup: Fruit Fly Mating, Airbnbs and Crime, and More

It’s not too often in a biologist’s career that she gets to experience evolution in action. But when Assistant Professor of Biology Yun Ding began studying the courtship behavior of a fruit fly species native to West Africa, that’s precisely what happened.

“Many species-specific traits are often ancient behaviors resurfacing under the right conditions,” Ding says. “At first, we were cautious in our claim of novelty, but our methods and analysis continually pointed to female wing-spreading behavior being a newly evolved novelty.” 

That research is one of four recent studies detailed below, in the first Omnia research roundup of 2025.

Fruit Fly Mating

A team of researchers led by Ding recently discovered a new courtship behavior in a species of fruit fly called Drosophila santomea native to an island off the coast of West Africa called São Tomé. In the newly observed behavior, dubbed “wing spreading,” females expand their wings outward to drive the courtship ritual, actively engaging with the songs of their male counterparts. 

“Our study suggests that behaviors are not always de novo creations,” Ding says, “but are often waiting to be unlocked in just the right way.” 

The scientists published their findings in the journal Nature Communications.

Airbnbs and Crime

An increase in the number of Airbnb properties in London led to an uptick in robbery, burglary, theft, and violence there, according to research published in the journal Criminology from David Kirk, Professor of Criminology, and University of Cambridge criminologist Charles C. Lanfear. 

One example the researchers provide deals specifically with robberies: They estimate that growing the volume of London rentals 10 percent over 2018 levels would lead to about 1,000 more robberies in a given year. “The explanation has more to do with the altering criminal opportunities in those neighborhoods,” Kirk says, “as opposed to the slow erosion of community cohesion and what criminologists call social control.”

 

Voting By Mail

In a Science Advances paper, a group of Penn researchers led by Marc Meredith, Professor of Political Science,and Michael Morse, Assistant Professor of Law, studied how rejected mail-in ballots get documented, what happens when a voter knows about a lost ballot in time and can subsequently vote in person, and why expectations that people’s votes may never make it where they need to go could deter use of the mail-in system for casting ballots.

Using Pennsylvania as a case study, the team drew several conclusions: For one, scholars should use caution when evaluating mail ballot systems based on the share of rejected mail ballots. Beyond that, giving voters sufficient time before an election to take corrective action can reduce lost votes. The findings, the researchers write, highlight the need for more research on the subject. Beyond that, “this research shows that Pennsylvania’s election rules cause thousands of ballots to go uncounted that would be counted in most other states,” Meredith says. “We hope that the state legislature considers our findings as it looks to improve these rules.”

Spending on Home Care

Even as states spend more Medicaid money on home-based care, the workers who provide the services aren’t earning higher wages. That’s according to findings published in the journal Health Services Research from Pilar Gonalons-Pons, Alber-Klingelhofer Presidential Associate Professor of Sociology, and colleagues from Penn Carey Law and the Perelman School of Medicine.

“We had expected one of two outcomes: Increased Medicaid spending would raise worker wages, or it would affect workforce size but not wages, if home care agencies hired more workers but didn’t raise their pay,” Gonalons-Pons says. “The results didn’t fit neatly into either outcome.” Rather, the researchers found that between 2008 and 2019, average state spending jumped from $773 million to $1.5 billion, but worker wages stayed put at around $11 or $12 an hour.