The endocrine systems of isolated and crowded Locusta and Schistocerca in relation to oöcyte growth, and the effects of flying upon maturation

In isolated Schistocerca and crowded Locusta, oöcyte growth is slow compared with that in crowded Schistocerca and isolated Locusta. Slow oöcyte growth in both species is correlated with an accumulation of material in the pars intercerebralis-corpora cardiaca neurosecretory system. Release of neurosecretory material is prevented in isolated Schistocerca by the absence of adequate stimulation, and in crowded Locusta by the action of some inhibiting agent. Daily flying on a roundabout accelerates the rate of oöcyte growth in crowded Locusta and in isolated and crowdedSchistocerca, but apparently has little effect upon the growth of the oöcytes in isolated Locusta. Where it occurs, the increased rate of growth of the oöcytes is correlated with the more rapid release of material from the neurosecretory systems of the locusts. The effects of flying and crowding in Schistocerca together equal the stimulating effect of the male pheromone, but the effect of flying in Locusta opposes the inhibitory effect of crowding. Cyclic changes in the volumes of the corpora allata are correlated with oöcyte growth in flown and unflown, isolated and crowded Schistocerca and seem to follow upon the activity of the neurosecretory system, the greatest volume of the glands being attained sooner in the flown than in the unflown females. In isolated Locusta, the pattern of volume changes in the corpora allata is identical in both the flown and unflown females and is similar to that in Schistocerca. In unflown crowded Locusta, the corpora allata increase greatly in size without any corresponding oöcyte growth. Flying gradually reduces the size of the glands as the oöcytes develop. The enlarged glands in the unflown crowded Locusta probably represent a prolonged synthetic phase without concomitant release of hormone.