Abstract
Ditrysia are the largest lepidopteran clade comprising about 99% of the order's species richness (Kristensen & Skalski 1998). Currently, the group is classified into three superfamilies (Tineoidea, Gracillarioidea, and Yponomeutoidea) plus the large clade Apoditrysia (van Nieukerken et al. in press). A number of 20th century authors have studied morphological features of the second abdominal sternum (sternum II) in Ditrysia, particularly how the various sternal processes articulate with the metathorax (e.g., Borner 1939; Brock 1968, 1971; Kyrki 1983; Minet 1983, 1991). In the clade Apoditrysia, sternum II is highly modified, and this structure is considered the principal morphological synapomorphy supporting the monophyly of the clade (review: Kristensen 2003; see below for details).
NSTL