Oögenesis and oviposition of Zeiraphera diniana are stimulated by insemination and other factors. Unmated virgin females produce a primary stock of about 37 ripe eggs in their ovaries. Adequate space and/or nutrition will nearly double this number. Impregnation with viable sperm causes the maturation of another 30 eggs. This reaction is not correlated with the amount of spermatozoa present in the receptaculum, indicating an all-or-nothing effect. It is also independent of the rate of oviposition. Full stimulation of oögenesis, with the additional maturation of 60 eggs, is possible when oviposition is also fully stimulated. It is therefore concluded that a feedback mechanism between oviposition and oögenesis must exist. This mechanism has a positive influence on egg maturation when the majority of the eggs produced are laid. Whether or not it has a negative effect (i.e. suppression of oögenesis in the absence of egg deposition) is not yet clearly established. Oviposition is best stimulated by the presence of a green larch twig and by the transfer of a normal spermatophore into the bursa of the female. Each factor alone induces the laying of 20 per cent of the eggs; the two factors together, 94 per cent. Since intermediate values are obtained in mated females that have not been inseminated (spermatophores from highly irradiated males), it is concluded that oviposition is very problably stimulated by the seminal fluid within the spermatophore and possibly also by the presence of active spermatozoa in the receptaculum. The act of mating, and the mere physical presence of a spermatophore in the bursa, do not stimulate oögenesis and oviposition. © 1969.
