Photo/Illutration An alien cicada species inhabiting bamboo groves, whose body is slightly larger than that of the large brown cicada, is found in August 2017 in Kawaguchi, Saitama Prefecture. (Provided by Toru Usui)

KAWAGUCHI, Saitama Prefecture--When insect researcher Toru Usui went out to buy bamboo brooms at a hardware store and elsewhere in Ageo, Saitama Prefecture, he didn't have tidying up in mind.

Instead, he discovered cicada eggs among the brooms imported from China, in line with his suspicion on how the alien species had entered Japan.

Scientists primarily in Saitama Prefecture conducted DNA analysis of the cicada eggs and found that a Meimuna opalifera native to bamboo thickets on the Chinese continent has been proliferating in the prefecture and elsewhere.

A team comprising Usui, 66, an insect researcher in Ageo in the prefecture, and Masami Hayashi, 71, a professor emeritus of bug taxonomy at Saitama University, who is well-versed in cicadas, began research on the non-native species’ spread in the northern part of Kawaguchi in summer 2016.

The invasive bug has been heard making a loud metallic sound for one hour around sunset between July and August in and near Kawaguchi since around 2011. In addition, its chirping was reported in Aichi Prefecture and Kawasaki as well during the survey conducted until summer last year, according to the researchers.

Further research revealed that the non-native cicada’s habitats are scattered throughout the nation, but how it came to Japan was unknown.

Learning that eggs of the giant Asian mantis, an alien species native to China with an increasing presence in Japan, were spotted in Chinese-made bamboo brooms, Usui decided to investigate the cleaning tool as it was the likely cause of the mantis’ spread.

According to the agriculture ministry’s Yokohama Plant Protection Station, imported plants are quarantined to prevent the invasion by non-native pests but bamboo brooms are not subjected to the quarantine among other processed goods.

When the National Museum of Nature and Science’s specimen center in Tsukuba, Ibaraki Prefecture, carried out DNA analysis at Usui’s request, the identified genetic data was confirmed as the same as that of an adult cicada caught in Kawaguchi.

While the team’s findings were presented for the first time in the bulletin of the Japan Cicada Club in 2017, Usui and other members published their latest research results in the bulletin in November last year.

They concluded, “The sporadic presence of the cicada across the country can be explained if bamboo brooms are behind the phenomenon.”

Usui believes that the alien cicada “succeeded in proliferating in brooms left near bamboo thickets."

“They (imported brooms) could also provide a place for other foreign species as well as the cicada to hatch their eggs,” he cautioned.

Larvae of the cicada suck juice from subterranean stems of bamboo to grow to an adult measuring about 4 to 5 centimeters in length.

As no indigenous cicadas in Japan mainly inhabit bamboo groves, the foreign species is believed to rarely compete against Japan’s Meimuna opalifera and other native species.

However, as the cicada is regarded as a pest preying on bamboo juice in China, what impact the insect could exert on the local ecosystem will need to be studied in greater lengths in the future, according to the scientists.