[Postembryonic and regenerative growth of cerci and leg segments of Tachycines (Saltatoria)].

The postembryonic and regenerative growth capacities of cerci and legs were investigated inTachycines asynamorus. The normal length and growth of cerci and segments of the middle legs, and the number and duration of normal postembryonic instars were determined in isolated individuals. In the regeneration experiments, the animals were amputated after the molt into the second postembryonic instar.An organotypic cercus is regenerated after 2-3 molts. The increment of length between molts is about constant, normal length is never acquired. If amputation occurs within the first three days after the molt, a papilla or a small regenerate will usually be present after the next molt. The molting rate is decreased during the next 3-4 molts. If the amputation is performed later, no regenerate will usually appear until after two molts. In this case the average molting rate is not significantly decreased.An organotypic tarsus of the middle leg is present 1-3 molts after amputation, an organotypic tibiotarsus 3-4 molts after amputation. Normal proportions are reached after 6-8 molts. If the femur is also removed, no regeneration takes place. Seven potential steps of regenerative differentiation were distinguished. The earlier the amputation, the faster the regeneration. The total duration of development to the ninth instar is about the same in normal and regeneration individuals because in the latter the initial slowing down of molting is compensated by an increased molting rate after the fourth instar.The existence of certain organ-specific critical periods is postulated for each molt interval. Before such a period, regeneration may be elicited and can follow its autonomous course. After the critical period has elapsed, no regeneration blasteme can grow any more during that molt interval. There is evidence, that the critical period for cereal regeneration lies in the first half, for tarsal regeneration in the second half, and for tibiotarsal regeneration in the middle part of the molt interval. The pattern which happens to be determined in the epidermis blasteme, will become expressed in the cuticle through the process of molting.A comparison of the findings onTachycines, Carausius and some blattids leads to the following working hypothesis, inviting histological and further experimental analysis: Cerci have a proximal blasteme which exhibits proliferative growth during normal development and regeneration. In regeneration legs during segmentation the situation is similar, during growth after segmentation and during normal postembryonic growth, there is a self-regulatory control of limp proportions. The causes responsible for all types of growth are to be sought in the cycle of the hormonal system, and in the site and age specific competence of the cells.