More than one-fifth of old and nearly one-half of new jack pine budworm egg mass chorions remained on the foliage after one year, and an experienced observer could not determine accurately the age of one-fourth of them. Counts of new egg masses are used to estimate current populations, and large errors could result.
Batzer, Harold O. and Jennings, Daniel T.
"Persistence of Jack Pine Budworm Choristoneura Pinus Pinus, (Lepidoptera: Tortricidae) Egg Mass Chorions on Jack Pine Foliage,"
The Great Lakes Entomologist, vol 12
Available at: https://scholar.valpo.edu/tgle/vol12/iss2/6