juvenile hormone

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of several hormones in insects that regulate various physiological processes, especially larval development and reproduction.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Zo/'94l.) A hormone secreted by insects which inhibits the molting of an insect from its juvenile into its adult form; also, substances having similar activity, but produced by plants.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Any of a group of sesquiterpene hormones that regulate insect physiology by preventing molting of the exoskeleton and thus development of the larva