A number of families of insects can exert profound effects on trees, shrubs and wooden structures. Wood-eating insects often only do so in larval stage, but would be identified as flying organisms in adult form. Many lay their eggs on or within bark, leaves, buds or shoots, and the hatched larvae then spend some time feeding within the wood before maturing. "Primary invaders" are insects that target healthy trees and other plants; "secondary invaders" usually flourish in sick or dead ones.
Identify the wood-eating wasps called horntails by their typically bold, striking appearance. The horntails are a family of mainly nonstinging wasps that lay their eggs beneath the bark of expiring or just-expired trees. As they mature, the larvae feast within the heartwood, eating both the wood and an associated fungus often transferred by the adults. Horntails typically have large wings, stinger-like appendages used for "injecting" the eggs and strongly contrasting colour patterns.
Look for wood-boring moths, which are usually pretty distinctive from other insects. Pine tip moths, of which there are dozens of species in North America, show scale-covered, enormous wings (which are, when the insect is not in flight, sheathed like a cape over the body) and prominent, often feathery antennae. The moth larvae are the wood-eating stages, hatching from eggs laid on the exterior of conifers and then tunnelling into leaves or buds. Some other wood-boring moth species, like the cottonwood and boxelder twig borers, target deciduous trees.
Look for the rotund shape and hard, glossy bodies of bark beetles. They are relatively small compared to some other beetles--often well under an inch in length. Most are dark-coloured: The shothole borer, for example, is greyish black in hue, while the smaller European elm bark beetle shows a dark body with dull rufous or near-black wings.
Keep an eye out for the hefty size, cylindrical bodies and often flashy colouration of members of the longhorned beetle family. Larvae tunnel into wood for food and shelter. As Whitney Cramshaw notes in "Garden Insects of North America" (2004), some of the species in question are among the most robust of any insects on the continent. Types of tilehorned prionus, also called giant root borers, may be 2 inches long and armed with remarkably heavy, studded antennae. Those beetles are fairly drab in colouration, but others, like the painted hickory borer, are colourfully patterned, with a black body jagged with yellow stripes.
Recognise the metallic wood borers, another family of beetles, by their extended, flat bodies and glossy exoskeleton. Close to 700 species inhabit North America, targeting almost exclusively dying or dead trees.
Keep in mind that termites, perhaps the most universally known wood-eating insects, can fly in certain caste forms, though they are most familiar as wingless, subterranean, heavy-jawed soldiers and workers. The reproductive castes of most termite species exhibit two pairs of wings that are nearly equal in length and proportionately huge.