Prionoxystus macmurtrei

The combination of moderate size (45–75 mm wingspan), mottled gray-brown coloration, and spring-to-summer flight period distinguishes this species from many other Cossidae. It is smaller than the related carpenterworm (Prionoxystus robiniae), which has a wingspan of 50–90 mm. The similar species Prionoxystus piger is also larger (wingspan to 90 mm) and has been reported to have more contrasting wing patterns. Examination of genitalia or larval host association may be necessary for definitive identification in areas of overlap.

Adults have a wingspan of 45–75 mm. The body and wings are mottled gray-brown with irregular darker markings, providing cryptic coloration against bark. Forewings typically show a mix of light and dark gray with wavy transverse lines. Hindwings are lighter, often pale gray. The body is robust and somewhat hairy, typical of Cossidae. Antennae are bipectinate in males, simpler in females.

Associated with deciduous forests and woodlands containing ash, maple, and oak. Larvae occur within living or recently dead hardwood trees. Adults are often found near larval host trees and are attracted to lights.

Eastern and central North America: Ontario and Quebec south to Florida, west to Texas, north to Minnesota. Records also include Vermont.

Adults are on wing from April to July. The flight period spans spring through early summer, with peak activity varying by latitude.

Larvae feed on ash (Fraxinus), maple (Acer), and oak (Quercus). The specific tissues consumed are wood (xylem), with larvae tunneling through heartwood and sapwood.

• Fraxinus - larval food plantash species
• Acer - larval food plantmaple species
• Quercus - larval food plantoak species

Complete metamorphosis with larval development occurring within host trees. Larvae create extensive tunnels in wood, likely requiring multiple years to mature given the size of adults and wood-boring habit typical of Cossidae. Pupation occurs within the tunnel, with adults emerging through an exit hole.

Larvae bore into living hardwoods, creating tunnels that weaken structural integrity and degrade lumber quality. Adults are nocturnal and attracted to light. They do not feed as adults.

As a wood-boring insect, larvae contribute to nutrient cycling by breaking down hardwood tissue. They may also create habitat for other organisms in the form of abandoned tunnels. In natural forests, they likely target stressed, dying, or dead trees; in managed settings, they are considered a pest of living timber.

Considered a pest of hardwood timber. Larval tunneling reduces lumber grade and value, particularly in ash, maple, and oak. The species is not known to attack finished wood products or structures. Management in forestry contexts may involve removing infested trees.

• Prionoxystus robiniaeLarger size (wingspan 50–90 mm vs. 45–75 mm), also a carpenterworm moth with overlapping range and hosts. Previously confused or synonymized; now recognized as distinct.
• Prionoxystus pigerLarger size (wingspan to 90 mm), more contrasting wing pattern. Occurs in overlapping range.

• wood-borer
• pest
• hardwood
• nocturnal
• spring moth

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life