BARK or Engraver Beetles and Ambrosia Beetles

Family Scolytidae

Identification: Elongate, cylindrical. Head visible dorsally or concealed, narrower than pronotum. Tarsi short, 1st segment

BARK AND AMBROSIA BEETLES 205

not elongate. Antennae elbowed and clubbed. Brownish to black. 1-9 (mostly 1-3) mm.

Nearly all scolytids bore into bark or wood, both as larvae and as adults. Adults spend most of their lives in their burrows, leaving them only long enough to find a new host. Bark or engraver beetles burrow just under the bark; ambrosia beetles burrow into the heartwood and feed on fungi in the galleries. Bark beetles are very common and usually attack weakened, dying, dead, or recently cut trees; some attack living trees and since they often kill the tree are very serious pests, particularly in the West.

Bark, or engraver, beetles excavate patterns (galleries) under the bark, each species making a characteristic pattern. The adults

Monar thrum

(Anthonominae)

PINHOLE BORER (Cryptorhynchinae)

Scolyfus

Tachy-pterellus

Monar thrum

Scolyfus

(Anthonominae)

PINHOLE BORER (Cryptorhynchinae)

come in first and excavate 1 or more brood galleries, along the sides of which they lay their eggs; when the larvae hatch they bore away from the brood gallery, their galleries increasing in size as they tunnel, thus forming the typical pattern under the bark. Each species attacks a particular species of tree (or 1 of several related species). The galleries permit the entrance of fungi, which often rot the bark. The Elm Bark Beetle, Scolytus multistriatus (Marsham), is the chief vector of Dutch elm disease — a disease that has killed thousands of elms in the e. U.S.

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