An invasive paper-eating insect called ghost silverfish has been detected in museums and libraries across 19 prefectures in Japan, threatening valuable cultural properties. First found in the country in 2022, it reproduces parthenogenetically and multiplies quickly. The Tokyo National Research Institute for Cultural Properties urges facilities to act early.
Ghost silverfish, an invasive insect that nibbles at paper surfaces, was first discovered in Sri Lanka in 1910. Adults measure about 1 centimeter in length and pose a significant threat to historical items like ancient documents, byobu screens, and scrolls. In Japan, the pest was initially detected in 2022 across five prefectures, including Tokyo, Hokkaido, and Fukuoka.
Investigations by the Tokyo National Research Institute for Cultural Properties revealed that the insects are all female and reproduce parthenogenetically, allowing one individual to grow into a population of 20,000 in three years—a far stronger reproductive rate than typical silverfish. Eradication is feasible at temperatures of 10 degrees Celsius or below, or humidities of 43% or lower. However, museums and libraries maintain controlled environments to preserve books and artifacts, creating ideal conditions for the insect.
The institute reports that the spread to 19 prefectures likely occurred through unwitting transport in documents and packing materials. No damage to cultural properties has been reported so far, but preventive actions are essential. Recommended measures include storing documents in steel or plastic cases instead of cardboard, spraying pesticides on walls, frequent cleaning, and using poison bait. This month, the institute began supplying poison bait kits to affected facilities.
"Once ghost silverfish have gained a foothold, it becomes extremely difficult to get rid of them," said Yoshinori Sato, head of the institute's biological science section. "We'd like to stop their rise before they spread nationwide."