Botanical Glossary - Home

Pine White is one of the most destructive butterflies in the Pacific Northwest forest - in particular, it is the most important Pine defoliators.

The flight of the butterfly occurs in August, September and October. Emerald green eggs are laid upon Ponderosa Pine needles (or Lodgepole Pine and White Pine when in the same area as Ponderosa Pine) within a few hours after mating. These eggs are attached near the tops of the trees and are laid in rows at an angle of 45 degrees, with 5 to 20 eggs in each row. The winter is passed in the egg stage, and hatch the following June, or about the time new needles begin to appear on Ponderosa Pine. The larvae hatch from the eggs (small, pale green caterpillars with shiny black heads) - the young larvae feed in the clusters eating all the new needles until they mature into full grown larvae, which lower themselves to the ground via silken threads. They then attach themselves to low growing vegetation, transform to pupae, forming chrysalides. Within 15 to 20 days they emerge as adult butterflies.

Outbreaks of Pine White seldom last for more than 3 or 4 years, but the damage to the Pine trees can be devastating. One of the worst of these outbreaks occurred on the Yakima Indian Reservation in Washington during 1893 to 1895. Ponderosa Pine over approximately 150,00 acres was affected and from 20 to 90 % of the stand of Pines in this area was killed.

Fortunately, nature has provided a wasp-like parasite (Theronia Fulvescens) which lay eggs in the larvae, which feed until the parasite is mature, effectively killing the butterfly larvae.