Spruce Budworms Handbook: Techniques for Measuring Early-Larval Dispersal of Spruce and Jack Pine Budworms
- United States Department of Agriculture, Forest Service, Cooperative State Research Service
Early-instar larvae of the spruce budworm, Choristoneura fumiferana (Clem.); the western spruce budworm, C. occidentalis Freeman; and the jack pine budworm, C. pinus pinus Freeman, disperse periodically within and from their host trees. Some larvae disperse by crawling, but most dispersal occurs when the small larvae "spin down" from trees on silken threads. The larvae spin silk from glands located near their mouthparts. The silk threads are anchored to branches or other attachment sites and the larvae continue to spin silk as they descend from the tree. Frequently, the threads break at their points of attachment and larvae are carried by winds, sometimes for great distances.
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