The Ditrysia are a natural group or clade of insects in the Lepidopteran order containing both butterflies and moths. They are so named because the female has two distinct sexual openings: one for mating, and the other for laying eggs. About 98% of described species of Lepidoptera belong to Ditrysia. The group can be divided into basal or incertae sedis "micromoths" and the Apoditrysia which includes mostly larger moths as well as the butterflies. Those with a dorsal heart vessel belong in sect… (More on Ditrysia)