Question

Name the hormone responsible for development of caterpillar to moth
A. Juvenile hormone (JH)
B. Adrenaline
C. Thyroid hormone
D. Prothoracicotropic hormone (PTTH)

Answer 1

Insect hormone is responsible for the development of caterpillars to moth. The process by which caterpillars change to moth is known as metamorphosis e.g. butterfly, dragon fly etc. Complete metamorphosis occurs during a seemingly-dormant stage known as pupa.

Complete step by step answer: Insect have rigid exoskeleton and they only grow by shedding their exoskeleton. This process is called molting. Both metamorphosis and molting are regulated by different types of insect hormones. Molting hormone stimulates growth and helps in formation of cuticles. This hormone performs actions on the prothoracic gland, which in return secretes a steroid hormone called ecdysone. Same happens with metamorphosis. This process is also controlled by insect hormones as told earlier. In this process, juvenile hormone is secreted by the corpus allatum (gland present behind the brain). There are three hormones which play a major role in metamorphosis: prothoracicotropic hormone, ecdysone and juvenile hormone. When it comes to the last larval stage, juvenile hormone is no longer stayed. So it is not present in the adult stage. So the correct option is (D). Prothoracicotropic hormone (PTTH) is responsible for caterpillars to moth.

Note: Prothoracicotropic hormone abbreviated as PTTH secreted by neurosecretory cells present in the brain of larva. It is found in four groups: one in the left side of the brain, two in the middle and one in the right. As it is present in the brain also known as brain hormone. Activation starts in the brain only and after activation molting hormone is released. Ecdysone, a molting hormone is regulated by prothoracicotropic hormone.