The relationship between oviposition and spontaneous discharges of motor neurons in Bombyx mori

The experiments in this paper were planned to study the mechanisms of release of ovipositional behaviour in bombyx mori. For this purpose, egg-laying and the spontaneous discharges of motor neurons in G IX were compared between mated and virgin females. The spontaneous discharges of motor neurons in G IX were recorded extracellularly from the nerve bundles of the isolated G IX bathed in a mixture of Ringer's solution and body fluid.The mating stimulated egg-laying so definitively that within 24 hr from the removal of males the mated females laid most of the eggs stored in the genital organs. Ageing of the moth accelerated the egg-laying of the virgins: the number of unfertilized eggs laid by virgins within 2 days from emergence was 10 to 20 per cent of the number of fertilized eggs laid by the mated females within 24 hr, but the number of unfertilized eggs laid within 7 days by the virgins reached 60 to 70 per cent. On the other hand, mating activated the spontaneous discharges of motor neurons in G IX. Moth age had a slight effect on the spontaneous discharges of motor neurons in G IX of the virgins.In recording the spontaneous discharges of motor neurons in G IX, the only changed factor was the body fluid outside the ganglion itself. Therefore, it was postulated that mating changed the humoral condition of the female. This change may stimulate the motor neurons in G IX, and then the egg-laying of mared females may be activated.