de Jong et al. (1996) and Ackery et al. (1999) could not find morphological evidence for keeping Megathyminae apart from
Hesperiinae. The separation was only based on autapomorphic characters of Megathyminae directly related to the boring habit of the larva: larval and adult head relatively small and larva without a “neck” (a narrow part of the body directly behind the head facilitating movement when living between leaves spun together). The combined morphological and molecular study by Wahlberg et al. (2005) did not include Megathymus, but two species of the supposed subfamily were included in the molecular study by Warren et al. (2008). They both ended up internal to the Hesperi-inae and the same was the case when morphological characters were added (Warren et al., 2009), so in this case morphological characters and molecular characters supported each other in downgrading the Megathymus and allies.