imaginal disk development development of the genital imaginal disk IDOMAL:0002428 IDOMAL:0002428 In Aedes stimulans larvae of both genotypes an imaginal disk appears, during the 3rd instar, as a medial pair of epidermal thickenings in the posteroventral region of the 8th abdominal segment. During the first half of the 4th instar cell division occurs in these thickenings and in the area between them, and the disk develops into two lateral podal buds and a median plate. idomal_namespace