Correlations of the seasonal counts of the hypopi of lardoglyphus konoi (Sasa and Asanuma) formed in laboratory cultures to atmospheric humidity and temperature were estimated and found not to be statistically significant. By another series of experients it was found that overcrowding and food scarcity were also not responsible for hypopus formation. It is suggested that the ability of the protonymphs to transform to hypopi may be hormone-dependent and that the variability in this respect among protonymphs of the same population or in different species may be due to variation in internal composition and in capacity to respond to the external factors by producing the hormone or hormones concerned.