Lab Core

Tobacco Hornworms


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Description of Research System

Manduca sexta Life Cycle Stages I: Egg Through Fourth Instar

Adult female moths lay their eggs on the leaves of tobacco, the food of the specialist larvae. The larvae proceed through four or five instars, molting between each instar. In the larval stages, the cuticle over most of the organism is somewhat flexible, allowing for growth in length (and weight) between molts. The head capsule is a region of inflexible cuticle, and must be shed prior to increasing in size.

 

A Manduca sexta egg. Eggs are approximately 1 mm in diameter, making them easily visible on toabcco leaves. They are usually blue-green to yellow-green in color. The first instar larva hatches out after 1-3 days.

Examples of instars 1 through 3. It is often difficult to distinguish between these early larval stages.

Two fourth instar hornworms. Just prior to molting, the head capsule is often shifted at an angle to the rest of the body. The head capsule of the hornworm on the right has "slipped" in this way.

On to the fifth instar


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March 1999