Lincoln County Clerk Suzanne McConnell says volunteers discovered the damage as they were working to digitize old, paper records, including court judgments, birth certificates, marriage licenses, land deeds and permits. The records - some dating back to the 1930s - were all kept in the vault below the county courthouse.
In response, the county will fog the area with pesticide to protect against any future damage.
"All the other records we've opened up are in good shape," McConnell told The Times News in a story published Wednesday.
At least two books of documents have been permanently destroyed by bugs that appeared to have tunneled through pages.
The setback hasn't stalled the process of putting the rest of the county's older records in digital form. McConnell said that process could take another four to six weeks.
Lincoln County is relying on FamilySearch, the world's largest repository of free genealogical records. The company also manages the Family History Library in Salt Lake City.
The company has already digitized records for several Idaho counties. While digitizing records may be time consuming, Lincoln County Commissioner Roy Hubert says counties have an obligation to preserve all public records and documents.
"It's a responsibility of the county to have permanent records and keep them in good shape," Hubert said. "I would encourage Idaho counties to go over their own records to make sure they're in good shape."