Influence of Illumination on Moulting and Regeneration in the Cockroach Blattella germanica (L.)

Abstract

IN Blattella germanica, at temperatures between 18° and 30° C., regeneration of a metathoracic leg, if begun before the critical period, adjusts the moulting cycle so as to provide the exact amount of extra time needed for completion of the regeneration process before ecdysis1–4. (If the level of regeneration is such as to require no muscular reorganization, this effect is absent5–7.) In animals regenerating a whole leg, but not in controls, the corpora allata and ‘head lobes’ (ventral glands) show marked volume oscillations suggesting a circadian rhythm5,11. Photoperiod effects are important in re-setting timing of developmental processes in the diapause of many insects8, and the onset of the dark phase in particular influences circadian activity rhythms, neurosecretion, and abnormal morphogenesis leading to tumour formation in the cockroach Periplaneta9. Far-red illumination has an adverse effect on growth in B. germanica10.