I recently identified pine needle scale on white pine. The following is information about the life cycle of this common pest.
The pine needle scale, Chionaspis pinifoliae (Fitch), is probably the most common armored scale found on conifers in the United States and Canada. The white, oystershell shaped scales can completely cover needles, causing plant discoloration to needle and branch death.
This scale settles on the needles of its host and forms white, oyster shell-shaped wax covers. These covers or armor are about 1/16 to 1/8- inch long when the scales are fully grown and there is a yellowish spot, the exuvim, on the small end. The male scales are usually smaller and more slender. This scale overwinters as deep reddish colored eggs protected under the female's old armor. The eggs hatch in mid-May into tiny, flat nymphs called crawlers. These crawlers creep to new places on the tree in order to find suitable needles on which to feed. These clumsy crawlers often fall from the trees and may be blown onto nearby trees. Once settled on a suitable needle, the crawler inserts its hair-like mouthparts, and begins to form the new armor. After a couple of weeks, the nymph molts under the armor and continues to increase in size for about three weeks. By this time male scales are smaller and more slender than the females. The males molt into a pre-pupa for a week before emerging as winged adults. The females, however, molt into wingless nymph-like adults. After mating, the females continue to grow for a couple of weeks before laying eggs under the armor. Females produce an average of 40 eggs.
Two generations of this scale occur. The overwintering eggs hatch in mid-May and the summer produced eggs hatch in late July. Unfortunately, the eggs may hatch over a period of two to three weeks.
Information from the Ohio State University http://ohioline.osu.edu/hyg-fact/2000/2553.html