The insert, labeled "carb"-TE, is a class II transposable element that has an approximately 9-kb non-repetitive sequence that is tandemly repeated two and a third times. There are 6 base pairs of inverted repeats and duplicated 4 base pairs at the target site that is not present in "typica" moths. "Carb-"TE has higher expression during the stage of rapid wing disc morphogenesis. The mechanism of how it increases expression or if it is the only gene involved is still not known.