Gnathotrichus sulcatus (Scolytidae)

the scratch-faced ambrosia beetle


Gnathotrichus sulcatus, the scratch-faced ambrosia beetle, newly emerged adult. Approximately the same length as T. lineatum but more slender. The beetle is uniformly shiny brown when newly emerged from pupa. The exoskeleton darkens as the adult matures before flying to a new host. The head is less distinct from above than T. lineatum.


Gnathotrichus sulcatus, the scratch-faced ambrosia beetle, gallery, eggs, and early instar larvae. Gallery with eggs and early instar larvae and larval niches.

Aspects of life in a log for Gnathotrichus can be seen in a video clip taken from the film, Tiny Beetles - Expen$ive Ta$te$.


Gnathotrichus sulcatus larva in gallery. Same as T. lineatum except entrance hole is smaller diameter and galleries are often branched in G. sulcatus. Shape of wood boring particles can also be used to distinguish attacking genus. Gnathotrichus adults overwinter in the log.

Principal Hosts:

Nearly all western coniferous species.

Economic Importance:

Gnathotrichus beetles spend their whole life cycle inside a log. They emerge to search briefly for new logs to attack and set up new galleries. This long period in logs means they can be in lumber before it is milled and continue development while on the way to market. Gnathotrichus is the most frequently intercepted ambrosia beetle in Canadian lumber imported into Australia.

G. sulcatus also attacks green lumber in sawmill yards which greatly adds to the quarantine problem in export markets. G. sulcatus and G. retusus together are a distant second in importance to T. lineatum.

The economic importance of the damage caused by the beetles is demonstrated in a video clip from Tiny Beetles - Expen$ive Ta$te$.

References and Links:

EAG: 518, 520; FC: 380-382.

See HForest.

Additional Images:

Larva and pupa of G. sulcatus Adult G. retusus boring new gallery G. sulcatus gallery in sapwood Maturation feeding by new adults extends lateral niches