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Under optimal conditions, adult firebrats moult about every 9 days (English strain) or 13 days (American strain), irrespective of age, sex, or reproductive activity. The epidermis is activated on the 4th or 5th day of the 9-day stadium and the deposition of the cuticle follows 2 days later. There is a critical period for the secretion of a brain hormone on the 5th or 6th day of a 13-day stadium, equivalent to the 3rd or 4th day of the 9-day stadium; maximal activity in the ventral gland coincides with or follows shortly after this, also coinciding with the activation of the epidermis. Thus the control of moulting in Thermobia closely resembles that in the pterygotes.

The female firebrat must mate before she can complete the terminal stages of vitellogenesis. Mating is followed by an increase in stainability of the median neurosecretory cells, and by increased rates of RNA and protein synthesis in these cells. The volume of the corpus allatum, corrected for differences in size among firebrats, increases approximately 70 per cent after mating due to an increase in cell number and to increase in the volumes of both nucleus and cytoplasm. Increased RNA and protein synthesis accompanies these changes in volume. Extirpation of the corpora allata, and the implantation of corpora allata from Periplaneta americana , confirm that these glands stimulate yolk deposition. The results also indicate that the corpora allata can regenerate, and that wounding, or premature initiation of the moulting cycle associated with it, can inhibit vitellogenesis.

Ovarian changes which accompany the changes in the rate of oviposition in founding females of Hodotermes mossambicus involve alterations in the number of ovarioles in which yolk deposition occurs, and in the proportion of oocytes which enter the final stage of maturation.

Under optimal conditions, reproduction does not affect the rate of growth in female Lepisodes. In unmated male and female firebrats, an increase of weight after ecdysis is associated with a single phase of feeding activity, which terminates near the middle of the instar, coincident with the reconstruction of the midgut epithelium. In mated females, a greater increase in weight accompanies a more intense first phase of feeding, and at oviposition a short second phase of feeding commences. The weight of food consumed in this second phase is closely correlated with the weight of eggs laid, and evidently compensates for loss of reserves at oviposition.