Insect Development: Complete Metamorphosis

Insects exhibit a diverse array of developmental strategies.  The development most commonly associated with insects is the life cycle of a butterflies in which an egg hatches into a caterpillar, the caterpillar creates a cocoon or chrysalis, and then the adult butterfly emerges.  This type of development exhibited by butterflies is termed holometabolous development.  Many insects exhibit holometabolous development such as beetles (Coleoptera), flies (Diptera), Dobsonflies (Megaloptera), and a number of other insect orders.  Insects that have complete or holometabolous development look vastly different when comparing larval forms and adults.  Also all holometabolous insects have a pupation period where physiological changes occur in the last instar that lead to adult characters.

Confused Flour Beetle Life Cycle (Baldwin & Fasulo, 2014)

Control of when to pupate or molt is largely controlled by the hormones ecdysone and juvenile hormone.  As the name implies, juvenile hormone promotes larval characteristics and inhibits molting or pupation.  By contrast ecdysone promotes molting, pupation, and the development of adult characteristics (Meyer, 2006).  For a more thorough introduction to molting and the hormones associated with it visit this link. 

Works Cited: 

Baldwin, R. & Fasulo, T.R. (2014) "Featured Creature: Confused Flour Beetle".  http://entnemdept.ufl.edu/creatures/urban/beetles/red_flour_beetle.htm

Meyer, J.R. (2005).  "The Endocrine System: Hormonal Control of Molting & Metamorphosis" North Carolina State.  http://www.cals.ncsu.edu/course/ent425/tutorial/endocrine2.html