[Experimental investigations on the postembryonic differentiation and the regulatory capacities of the male genital imaginal "Anlagen" inLymantria dispar L. (Lepidoptera) : I. Morphogenesis of the male genital armature].

1. This study deals with the postembryonic development of the male genital armature inLymantria dispar. 2. The Herold's organ, a ventro-median, sak-shaped, epidermal invagination of the 9th abdominal segment, is already present in the newly hatched larva. It is linked to the testes by two mesodermic strands (the future vasa deferentia). 3. In the 3rd stage larva (total number of stages: 7) the lateral walls of the proximal part of the Herold's organ starts to develop primary lobes. 4. Beginning with the 7th day of the last larval stage, the primary lobes are subdivided into two pairs of secondary lobes. The proximal lobes represent the "Anlagen" of the aedoeagus and the ductus ejaculatorius, the distal lobes represent the "Anlagen" of the valvae. 5. Before the onset of the pupal phase (9th day of the last larval stage), the fuson of both aedoeagus-lobes gives rise to the unpaired aedoeagus-"Anlage". During the prepupal phase the valvae-lobes are translocated to the body surface. 6. Beginning with the 2nd day of the pupal phase the valvae-"Anlagen" grow rapidly and differentiate into the valvae-basis and the valvae-hook. Abdominal segments No. 9 and No. 10 undergo reduction and are drawn into the segment No. 8. The aedoeagus-"Anlage" appears at the body surface; the anellus is formed. 7. The chitin ring develops from the pleurals and from the tergum of the 9th abdominal segment. The saccus is formed by invagination of the epidermis at the borderline between the segments No. 8 and 9. The uncus derives from paired "Anlagen", which are recognizable lateral of the anal groove in the 3 days old pupa. They develop during the reduction of the pupal cone and the outgrowing of the anal cone and fuse to the unpaired uncus. 8. At the 9th day of the pupal phase, the morphogenesis of the genital armature is completed and is followed by the histogenesis.