Biological performance of the white pine weevil in relation to the anatomyof the resin canal system of four different host species

The anatomy of the resin canal system was observed on lateral branches of f our host species of the white pine weevil (Pissodes strobi Peck) in relatio n to weevil performance. The host species studied were Norway spruce (Picea abies (L.) Karst.), white spruce (Picea glauca (Moench) Voss), red spruce (Picea rubens Sarg.), and white pine (Pinus strobus L.). Survival, number, and mass of adult weevils were measured on attacked terminal leaders collec ted before adult emergence. One uppermost lateral branch was collected at t he base of each attacked leader. Cross sections of these lateral branches w ere observed to measure the number, diameter, depth, and density of inner a nd outer resin canals. Nearly all resin canal measurements differed signifi cantly among species, with white pine differing greatly from the other spec ies with larger canals and lower canal density. Correlation analysis demons trated that the anatomy of the resin canal system was principally related t o adult mass, with the most important variable being the density of inner c anals (r = -0.54). Trees characterized by low density of large inner resin canals, like white pine, seemed to favour mass gain in adult weevils. The p resent study suggests that a high density of inner resin canals constrains the insect to feed on canals early in larval development, which subsequentl y reduces weevil mass.