[Experimental investigations on the regenerating and regulating capacity of the wing imaginal disks inLymantria dispar L. (Lepidoptera)].

1. The regulating capacity and the state of determination of the regions of the wing joint on the imaginal disk in the last two larval stages are examined. 2. After dissection of a part from the wing imaginal disk on the second and fourth day of the last larval stage, regeneration is initiated, but not completed because the remaining time period before the prepupal stage begins is too short. From tests made on the second day of the final larval stage some of the implanted medially halved wing disks will form symmetrically duplicated parts. 3. On the fifth day of the last larval period regeneration did not appear in all cases. The regulating capacity disappears after the fifth day. The period of determination may lay between the fifth and the sixth day of the last larval stage. 4. After extirpation of a medially halved wing disk during the penultimate stage, the remaining half wing-Anlage, apart from the joint elements, even the wing lamina will be partly or completely regenerated. 5. The parts of the imaginal disks, implanted in the abdomen, duplicate themselves in many cases but were not able to regenerate a complete wing joint. Such double formations appeared often, but not always symmetrically. Even the tegula can be doubled. 6. When regeneration has begun, if at all present, a delay in further development does not occur to the same extent inLymantria as inEphestia.