부산대학교 도서관

Stands of black spruce, Picea mariana(Mill.) B.S.P., in Northern Manitoba and Saskatchewan were defoliated by insects from 1954 to 1955 (Prentice and Hildahl, 1955). The defoliation was sufficient to show reddening of the tops from the ground as well as from aircraft at an elevation of 1,000 feet. Collections showed clearly that the most abundant species was the black-headed budworm, Acleris variana(Fern.); larvae could be found at all crown levels. Other species of insects were also common in the tops of trees with dense compact foliage such as often found in “club-tops” of black spruce. The reddening of foliage was not noticeable after the decline of the black-headed budworm populations in 1956, but the numbers of the other insects, which formed a “complex” of species, persisted at varying levels of abundance in the tops of black spruce.