Japanese researchers say an insect has likely expanded its habitat on an uninhabited volcanic island located far south of Tokyo.

Frequent volcanic activities have been observed since 2013 on Nishinoshima Island in the Ogasawara Island archipelago.

The entire island was covered by volcanic lava and ash during a major eruption that occurred about four years ago. Researchers thought the eruption had exterminated all life on the island.

But a type of earwig was found in an annual field survey of the land and waters around the island conducted by the Environment Ministry last year.

The same kind of insect was found at a different location during this year's survey.

The insect was known to have lived on the island before the eruption.

The ministry plans to survey a wider area on the island as it believes the insect's habitat has been expanding.

The researchers have also found that the number of boobies sharply decreased by about 80 percent from last year. They suspect the birds' reproduction rate may have slowed as volcanic ash continues to fall.

The ministry plans to continue its survey and analysis on the island.