. An annotated list of the important North American forest insects. Forest insects. DEFECTS IN TIMBER CAUSED BY INSECTS 39 DEFECTS CLASSED AS BLACK CHECK "Black check" is the hiinbernian's name for a common defect consistin<2: of a dark stain in the heartwood and sapwood, surrounded by thickened, curled, or abnormal layers of wood (fi<^. 41) (6"). It should not be confused with stains associated in the wood with other boring insects (as ambrosia beetles), wdiere the wood is rarely dis- torted. Although also caused by other agents, it particularly applies to the defect in w
. An annotated list of the important North American forest insects. Forest insects. DEFECTS IN TIMBER CAUSED BY INSECTS 39 DEFECTS CLASSED AS BLACK CHECK "Black check" is the hiinbernian's name for a common defect consistin<2: of a dark stain in the heartwood and sapwood, surrounded by thickened, curled, or abnormal layers of wood (fi<^. 41) (6"). It should not be confused with stains associated in the wood with other boring insects (as ambrosia beetles), wdiere the wood is rarely dis- torted. Although also caused by other agents, it particularly applies to the defect in western softwoods (hemlock, fir, spruce, and yellow pine) produced by the maggots of several small flies ^^ or moths,^^ but the term is also used for a somewhat similar defect in oaks produced by the larvae of large beetles.*^ (Figs. 42 and 43.). Fig. 42.—Pile of logs with grub lioles made by round-headed borer {Bomalciim rufulum). This defect is considered as " wormholes, no living -worms or decay" These defects are caused by the insects injuring the growing tissue of the tree and killing a small area of the outer layers of wood. The subsequent growth of the tree finally heals over this injury, but many annual layers are stained and distorted. The original small j)ocket or cavity where the insect was working remains, and in conif- erous trees it fills up with pitch. Western hemlock contains more of this injury than any other soft- wood. In quarter-sawn (vertical-grain) wood the checks appear as small seams one-half to 1 inch long, with one side curly, while in bastard-sawn (flat-grain) boards they appear as oval or rounded spots from one-half to 1 inch in diameter. The defects in other conifers are similar but not so numerous. 38 Cheilosia spp. " Parharmonia. *" Romaicum sp. and Goes Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrati
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