Decreased number of nymphal stadia in the lygaeid bug, Dimorphopterus japonicus (Heteroptera: Lygaeidae).

The lygaeid bug, Dimorphopterus japonicus , is a common species in Japan which feeds mainly on the eulalia, Miscanthus sinensis. It shows a marked wing dimorphism of brachyptery and macroptery. Almost all species of the Heteroptera pass through five nymphal stadia, although some exceptions have been noted. In the present study, we observed that D. japonicus had four nymphal stadia before eclosion to adults, while Dimorphopterus pallipes , a closely related species, had five. The number of stadia in D. japonicus did not vary irrespective of sex or wing morph in our observation. This is the first report of a four stadia life cycle in lygaeid bugs. In addition, phytophagous species having a four stadia life cycle are uncommon in the Heteroptera. Although the reasons why D. japonicus has only four nymphal stadia remain unknown, it may have evolved from an ancestral species with a five stadia life cycle like D. pallipes.