Abstract
The larvae of Dioryctria abietella (D. & S.) are among the most destructive pests of the cones of slash pine, Pinus elliottii Engelm., and longleaf pine, Pinus palustris Mill., in the Southern United States. Larval instar data have been particularly useful in laboratory insecticide screening tests where it is essential to use larvae of the same age. The following is a brief account of a test to determine the number of larval instars of D. abietella in Florida.