Research System Home Page

Description of Research System

• Life Cycle Stages
  
  
• Raising M. sexta
  
  
• Cell/molecular investigations
  
  
• Ecological/
  physiological investigations

Manduca sexta Life Cycle Stages II: The Fifth Instar

The fifth instar, the last before pupation, brings the most changes to the hornworm. The hornworms grow a great deal during the fifth instar. Near the end of the fifth instar, a new "wandering" behavior is noticeable in the hornworms. They move down, away from light; if they are in food, they begin burrowing through the food. Around the same time, their dorsal blood vessel becomes visible through their dorsal wall, and it is easy to see it pulsing. By the end of the fifth instar, the hornworms actually diminish slightly in size as they finish eating and begin preparing their pupal case.

	This brand new fifth instar hornworm still is showing remnants of its fourth instar cuticle, which is being shed off of its hind end.
	All three of these hornworms are in the fifth instar. The top hornworm has molted fairly recently. The middle hornworm is close to exhibiting a pulsating dorsal blood vessel. The bottom hornworm has begun decreasing in size, and will form it's pupal case very soon.
	This is an example of "wandering" behavior; the hornworm is barely visible in its plastic food cup, buried amongst its food and feces.

Back to the egg and early instars	On to the pupa and moth

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March 1999