Bark Beetles

(Ipidae or Scolytidae), a family of beetles. The body is cylindrical, brown or black, and usually quite small (0.8–12 mm). The bark beetle has clubbed antennae and legs with four joints. The elytra in many species of bark beetles have a depression in the back that makes passages in plant tissue. There are two subfamilies—Scolytinae (with a single genus) and Ipidae—and more than 3,000 species. In the USSR there are more than 300 species. They are particularly diverse in the taiga zone, Caucasus, and southern Far East.

All bark beetles live under the bark or, more rarely, in the bark, wood, or roots of trees. Occasionally they live in the stems of herbaceous plants; some tropical species live in fruits and seeds. Many species cause major damage to forests, orchards, and parks. Most bark beetles live on trees of a particular genus or species, usually only on the trunks or branches; some live in dense, and others in sparse, forests. Only a few species are polyphagous. Bark beetles remain hidden most of their lives, flying only when the time for laying eggs approaches. For egg-laying the beetles bore an entrance into the bark; the entrance is connected to the “nuptial chamber,” where the male mates with one or more females. Leading away from this chamber are “mother galleries” (the number depending on the number of females), with egg chambers in the walls. Larval tunnels lead from the egg chambers, ending in pupal cells. The young beetle bores its way to the surface from these cells.

Most bark beetles attack weakened trees, but a number of species attack perfectly healthy trees, particularly during massive reproduction. Trees infested with the beetles die quickly. Bark beetles are also carriers of certain diseases, such as Dutch elm disease and blue rot. (The latter greatly reduces the quality of wood.)

Controlling bark beetles is difficult. The main method is to remove windfalls and material remaining after tree-felling and to cut out infested trees. In the USSR the most harmful species are Blastophagus piniperda, B. minor, and Ips typographus, which attack conifers, especially spruce; Ips sexdentatus, which infests pine and cedar; the European spruce beetle (Dendroctonus micans), which attacks Oriental spruce; and Xyleborus dispar, which infests many deciduous trees.