Abstract
Luciola parvula (Coleoptera, Lampyridae) is a terrestrial firefly species widely distributed in Japan. Previous studies reported that there were two ecological morphs of adults of this species: large and small morphs. However, the procedure used to identify the two morphs has remained ambiguous and confused. The present article provides a brief review of the two morphs in this species and then proposes an allometric approach to detect the existence of the two morphs.