Monochamus sartor (Fabricius)

Coleoptera: Cerambycidae

IDENTIFICATION

These shiny, black metallic beetles are 21 to 35 mm long and have sparse yellow hairs on the elytra.^{2, 25, 128} Antennae are twice the body length in males but only slightly longer than the body in females.² Antennae of both sexes are black but the bases of the 3^rd to 11^th antennal segments in females are whitish-gray.^{2, 25} A distinguishing characteristic of this species is a transverse saddle-like impression found behind the pronotum.² The pronotum and elytra of females have a few white spots, but these are absent or indistinct on males.²⁵ Female elytra have parallel edges whereas the male's narrows posteriorly.²

HOST TREES

Picea (main host), Abies, Larix and Pinus.^{2, 25}

LOCATION OF INFESTATION WITHIN THE TREE

Larvae feed on the inner bark, sapwood and heartwood along the stem. Attacks usually occur 2 to 4 m above the ground.^{2, 25, 85} Immature beetles maturation feed on needles, green cones and twigs.^{2, 25, 128}

HOST CONDITION

Weakened, felled, fire scorched, or uprooted trees.^{2, 25, 85, 128} Large diameter stems are preferred.^{25, 85} As populations increase during an outbreak, attacks can occur on healthy trees.²

DISTRIBUTION

Europe.^{2, 128}

SIGNS AND SYMPTOMS

Beetles emerge in spring and feed in the crown on needles, weakened twigs and green cones.^{2, 85, 128} In the summer, fertilized females excavate a funnelshaped pit in the bark, 6 to 7 mm wide and 4 to 5 mm long, and deposit a single egg in each niche.^{2, 85, 128} At least 50 eggs are laid by a single female.⁸⁵

Early instar larvae excavate large, deep, galleries (up to 50 cm long) packed with long, fibrous frass in the inner bark.² Through an oval entrance hole, larvae bore horizontal galleries into the sapwood that may sometimes reach the heartwood.^{2, 128} Larvae then bore parallel to the grain of the wood for a few cm and expel frass through these holes.^{2, 128} Last instar larvae mine "U-shaped" galleries, so that adult emergence occurs on the same side of the trunk as the entrance holes.^{85, 128} Pupation chambers are plugged with wooden fibres and occur at a depth of 10 to 12 mm.² Adults emerge from exit holes 8 to 12 mm in diameter.^{2, 128}

A - Adult M. sartor (21-35 mm long).

B - Male and female M. sartor. Male antennae are twice the body length. Female antennae are slightly longer than the body.

C - M. sartor larva and larval galleries (up to 50 cm long). Note long, fibrous frass in the larval galleries.

Photo credits

• A Marcel and Alain Galant
• B Michael Hoskovec, Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic
• C Fabio Stergulc, University of Udin, Image 1433012, www.forestryimages.org, Feb. 5, 2004