Kazunori Yoshizawa, center, appears in an acceptance speech video delivered to the Ig Nobel Prize ceremony held at Harvard University on Sept. 14. (Provided by Kazunori Yoshizawa)

A team of entomologists from Japan and abroad won the 27th Ig Nobel Prize in biology for studying female insect genitalia that they say changes the definition of the word “penis.”

This year’s Ig Nobel prizes, awarded for research that “makes people laugh and think,” were announced at Harvard University on Sept. 14.

The research team includes Kazunori Yoshizawa, associate professor of systematic entomology at Hokkaido University, Yoshitaka Kamimura, associate professor of evolutionary biology at Keio University, and a number of international scholars.

The team found that female cave insects of the Neotrogla genus that were recently discovered in Brazilian caves have a penis-like organ that is inserted into the male bug during copulation.

The role-reversing insects are about 3 millimeters long and were registered as a new species around 2010.

In addition, the team found that one mating session between the bugs could continue for an impressive 40 to 70 hours.

During copulation, the male insect transfers nutrition, along with sperm, to the female penis. Yoshizawa and his team believe the physical makeup of the insects was created to allow the female to take control of the mating process to gain the nutrition.

There are about 5,000 different species in the order of Psocoptera, but only four in the Neotrogla genus in Brazilian caves were confirmed to have reversed genitalia.

“There is an element of simple surprise in this research that even children can understand--‘the girl insect has a willy’--and I frankly think it is interesting research,” said Yoshizawa, 46. “It can completely change general ideas we have about biological sex, and it also has significant academic implications in evolution and sexual selection.”

Some species, including fish, can change their sex out of necessity for survival. But the bug is the first species found to be born with reversed genitalia, the researchers said.

A paper on the finding was published in 2014.

The Ig Nobel judges praised the research because it prompts people to reconsider what makes a male a male and a female a female.

“This insect makes us wonder what a ‘female’ means and what a ‘male’ means, biologically,” said Kamimura, 40. “I would be happy if the research would make many people interested in the diversity of sex in animals.”

The researchers could not attend the awards ceremony at Harvard University because they have been hunting for similar Neotrogla species in caves on the Japanese islands of Kyushu and Shikoku.

Instead, they sent an acceptance speech video filmed in a cave in Kochi Prefecture to the ceremony.

“It is a great honor to receive an Ig Nobel Prize,” Yoshizawa said in the video.

One of his colleagues continued: “Every dictionary around the world explains ‘penis’ as a male structure. Our discovery has made billions of dictionaries outdated.”

(This article was written by Miki Morimoto and Tatsuyuki Kobori.)