State scientists say spicebush swallowtail caterpillar nests have been spotted in Berwick and Wells.

State wildlife authorities say there's been a sighting of a rare butterfly that was thought to have disappeared from Maine 75 years ago. Scientists say the spicebush swallowtail hasn't been seen here since a single adult was spotted in 1934.

This summer, Maine's Department of Inland Fisheries and Wildlife began a survey for the insect, concentrating on hardwood forests in Cumberland and York Counties, areas where the butterfly would be most likely to survive.

That effort paid off in mid-September, when several occupied swallowtail caterpillar nests were found in two spicebush swamps in Berwick and Wells. The discovery provided evidence that the butterfly is breeding in the area.

Scientists say the insect is an indicator of the health of enriched, temperate hardwood forests, which are increasingly threatened by development in southern Maine. Now that the butterfly has been found, authorities say further surveys will be conducted. They say the spicebush swallowtail could become a candidate for listing as one of the state's Endangered or Threatened species.