Fukuoka, Japan—University campuses are often places of learning and discovery, but rarely do researchers find a new species living right on their doorstep. However, that is exactly what happened when a research team from Kyushu University discovered a new species of ladybird beetle, Parastethorus pinicola, on a pine tree at Kyushu University's Hakozaki Satellite.
The discovery, published in Acta Entomologica Musei Nationalis Pragae , was part of a three-year study that revises the classification of the tribe Stethorini —a group of tiny ladybirds known for preying on spider mites—in Japan for the first time in over 50 years.
"I knew that this group of ladybirds often inhabits pine trees. Since there are Japanese black pines growing at the Hakozaki Satellite, I decided to look there, and that is where I found the new species," explains Ryōta Seki, a PhD student at the Entomological Laboratory, Graduate School of Bioresource and Bioenvironment Sciences , and the first author of the study. "Normally, insect collectors do not pay much attention to pine trees, which is perhaps why scientists have overlooked this species for so long."
The new species, named Parastethorus pinicola—meaning "pine dweller"—is a minute black beetle. It measures just over one millimeter in length.
"Small black ladybirds like these have not been studied much because they are incredibly difficult to identify," says Seki. "They are barely larger than a grain of sand, and they all look identical. You cannot tell the species apart without dissecting them and examining their reproductive organs under a microscope. Because of this difficulty, there were many misidentifications in past records."
To resolve these long-standing classification issues, the team examined approximately 1,700 specimens. In the process, they determined that the common ladybird known in Japan as Stethorus japonicus is actually the same species as Stethorus siphonulus, which is widely distributed from China to Southeast Asia.
The review also led to the discovery of a second new species from Hokkaido, named Stethorus takakoae. Seki dedicated this specific name to his grandmother, Takako Ōtsuki, to honor her steadfast support of his entomological pursuits since childhood.
"Standardizing these names is important because it allows us to share data and research with other countries in Asia," Seki notes. "It clarifies that this is a widespread species found from the tropics to temperate Japan."
For Associate Professor Munetoshi Maruyama of the Kyushu University Museum , who supervised the study, the discovery highlights the importance of looking closer at the world around us.
"People rarely notice such small insects. But as our study showed, even in a city or on a university campus, there are unknown species living right beside us," says Maruyama. "These 'minor' insects support our ecosystems. I hope this discovery makes people interested in the diverse and fascinating world that exists unnoticed at our feet."
(Written by Science Communicator Intern, Ken Eguchi)
