Usually, BMU boundaries will coincide with other administrative or operational boundaries. An early sign of attack by bark beetles. A high danger rating indicates that the area being considered is under attack by bark beetles or that attack is imminent, and that once attacked, damage will be high. Eggs are laid in niches or groups along the side of the egg gallery. When larvae hatch, they excavate feeding galleries in the phloem at right angles to the egg gallery.
Hazard is dependent on stand and site factors that are conducive to successful beetle attack.
In general, the higher the hazard, the more damage will occur during an infestation. Bark beetles normally have four larval instars between egg hatch and pupation. Bark beetle larvae are white, legless grubs. Typical adult features begin to form. Risk is dependent on the proximity of a beetle population to the stand in question.