Juvenile hormone (JH) is a vital group of acyclic sesquiterpenoid hormones that play a crucial role in regulating various physiological processes in insects. Discovered by Vincent Wigglesworth in the early 20th century, JH is primarily secreted by the corpora allata, a pair of endocrine glands located behind the brain. This hormone is essential for maintaining larval characteristics, regulating development, reproduction, and influencing behaviors such as diapause and polyphenism.

Key Functions and Mechanisms:

• Developmental Regulation: JH prevents premature metamorphosis by maintaining juvenile traits during molting, allowing insects to grow through successive instars. The levels of JH determine whether an insect will continue to develop as a larva or transition to pupation and adulthood.

• Reproductive Control: In adult female insects, JH stimulates vitellogenesis, promoting the production of yolk proteins necessary for egg development. This function is critical for ensuring reproductive success.
• Interaction with Ecdysteroids: JH works in concert with ecdysteroids, the hormones responsible for triggering molting. The balance between these hormones orchestrates the timing and nature of developmental transitions.

Research Applications and Clinical Significance:

• Insect Physiology Studies: Understanding JH's role provides insights into insect development and metamorphosis, contributing to our knowledge of life cycle strategies.

• Pest Management: Research into JH can inform pest control strategies. JH analogs are being explored as potential insecticides that disrupt normal development.
• Caste Differentiation: In social insects like bees and ants, JH influences caste determination and differentiation, shedding light on complex social behaviors within colonies.