1. Lees, A. D., The Physiology of Diapause in Arthropods (Cambridge University Press, 1955).
2. Danilevskii, A. S., Photoperiodism and Seasonal Development of Insects (Oliver and Boyd, Edinburgh, 1965).
3. Williams, C. M., Biol. Bull., 90, 234 (1946).
4. Williams, C. M., Biol. Bull., 103, 120 (1952).
5. Highnam, K. C., and Hill, L., The Comparative Endocrinology of the Invertebrates (Arnold, London, 1969).