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Unjoined bug does not molt

Unjoined bug molts into adult

Unjoined bug does not molt

Unjoined bug molts into adult

Join bugs with glass tube

Join bugs with glass tube

Vincent Wigglesworth Experiment
Both bugs molt into adults

Conclusion: A diffusible substance from the head region is necessary for molting.

42.3 A Diffusible Substance Triggers Molting The effect of time since the last blood meal on Rhodnius molting (experiment 1) led Sir Vincent Wigglesworth to hypothesize that some substance diffusing slowly through the insect's body stimulated molting. Further experiments (experiment 2) showed that molting is indeed controlled by a substance—a hormone—diffusing from the head.

ence of a blood meal in the digestive system). It makes sense, therefore, that the nervous system (the brain) should control the endocrine gland (the prothoracic gland) that produces the hormone that orchestrates all the physiological processes involved in development and molting (ecdysone). Later in this chapter we will see similar links between the nervous system and endocrine glands in vertebrates.

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Essentials of Human Physiology

Essentials of Human Physiology

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