Regeneration and the Moulting Cycle in. Blattella Germanica L. III. Successive Regeneration of Both Metathoracic Legs

Abstract

At 29[degree]C, 70% relative humidity, removal of the left and right metathoracic legs in succession, at intervals of 1,2, or 3 days, in first instar Blatteila germanica of known ages, results in the appearance at the first molt of (a) two asymmetrical papillae, the timing of the molt being undisturbed; or (b) a regenerate on the left and a papilla on the right side, the time of molting being determined by age at the 1st operation and independent of the 2nd; or (c) two asymmetrical regenerates, the time of molting being then determined by age at the 2nd operation and independent of the 1st. In (b) and (c) the rather constant size of regenerates from the 1st operation exceeds that of regenerates derived from either unilateral or simultaneous operations, while the smaller regenerates from the 2nd operation in (c) show wide but erratic variation in size, not regularly related to the timing of the operations or the molt. In about 2% of the material, the 2nd operation only gives rise to a structure intermediate between a papilla and a complete regenerate. Such rare exceptions to the "all or nothing" principle can appear only when ecdysis occurs during the exceedingly rapid process of differentiation of the blastema into a regenerated leg. This proceeds proximodistally in these individuals, in contrast to animals producing a regenerate and a papilla at their 1st molt, wher the rapid differentiation of the blastema contained within the papilla and its coxa occurs, early in the 2nd instar, in the opposite (i.e. distoproximal) direction. These results conform closely to predictions derived from the initial hypotheses put forward regarding the relationship between regeneration and the molting cycle. New information on the regeneration process was also obtained.