Eggs

• The female beetle will deposit eggs within the top eight to 12 inches of soil, depending upon her species. The eggs are white and shaped like a football and are only about 0.1 mm in length. The eggs will be laid in and around a crack in the soil in groups of 20 to 30 eggs. Many species will hibernate in this stage, though other species hibernate in their adult forms.
  
  

Larvae

• The larvae of most species hatch in the late spring or early summer. They immediately attach to the roots or corn and begin feeding. The larvae will go through three stages of development, known as instars. Each developmental stage lasts from a week to 10 days. From the first instar to the final, the larva -- or rootworm -- will grow in size from an eighth of an inch in length to up to a half inch in length.
  
  

Pupa

• Following the third instar, after about three weeks in the larval stage, the rootworm will prepare to pupate in the soil. During this stage, the rootworm is inactive and doesn't feed. The pupa is white and nearly translucent in appearance. Pupation will last about two weeks.
  
  

Adult

• The adult rootworm beetle emerges from pupae about July and has a life span of about a month after reaching this point in its development. When it emerges, the beetle digs to the surface of the soil and up the corn plant, where it begins feeding. Male beetles emerge from pupae before female beetles. The adult is about a quarter of an inch long.
  
  

Reproduction

• The female beetle will mate soon after emerging. She will then feed for about two weeks before going back to the ground to lay her eggs in cracks in the soil. Once she has laid her eggs, the female beetle remains on the ground and dies.