1. H. Laufer andH. Greenwood, Am. Zool.9, 603 (1969).
2. H. Laufer andT. K. H. Holt, J. exp. Zool.173, 341 (1970).
3. Larvae of these 2 species could not be separated from one another. The species were kindly identified by Dr.J. Knoz of the University in Brno.
4. The juvenoids were obtained through the courtesy of the Institute of Organic Chemistry and Biochemistry, ČSAV, Prague, and of the Zoecon Corporation, Palo Alto, California. The compounds were racemic mixtures; the aliphatic substances contained about 2/3 of the 2-trans isomers.
5. F. Sehnal andJ. Žďárek, J. Insect Physiol., in print (1975).