Greater Chestnut Weevil, Long Thought Extinct Since 1997, Rediscovered by University of Memphis Researchers

University of Memphis researchers have confirmed the rediscovery of the greater chestnut weevil, a beetle long believed to have vanished after the near-loss of the American chestnut in the early 20th century.

Professor Dr. Duane McKenna, director of the University of Memphis Center for Biodiversity Research (CBio), and doctoral candidate Michael Charles identified the insect after noticing images on iNaturalist that resembled the species. Charles said the last confirmed sighting dated to 1997.

How the Rediscovery Unfolded

Photos on the public platform iNaturalist prompted targeted fieldwork. Charles collected larvae from suspected host trees, sequenced their DNA, and compared the results with historical museum specimens. The genetic match confirmed that the greater chestnut weevil is extant.

Distinctive Biology

The greater chestnut weevil is notable for extraordinarily long mouthparts — reportedly longer than its body — which it uses to bore into chestnuts for feeding and egg-laying.

“For decades, the greater chestnut weevil was considered a classic example of coextinction — the loss of dependent species due to the decline of their hosts,” said McKenna. “Its rediscovery is a rare piece of good news in the broader biodiversity crisis, and a reminder that we have only a brief window to find and protect species that are quietly slipping toward extinction.”

“This rediscovery wouldn’t have been possible without the observations of volunteers and the digital tools that connect their data to scientists,” said Charles. “It shows how anyone with a smartphone can help us detect species at risk of extinction and make a real contribution to biodiversity research and conservation.”

While this finding is encouraging, the researchers stress that it is not a sign the species is secure. Continued monitoring, habitat protection, and further study will be necessary to determine the beetle’s distribution, population size, and conservation needs.