Macremphytus tarsatus

Distinguished from caterpillars (Lepidoptera larvae) by having six or more pairs of prolegs rather than five or fewer. The white waxy coating of intermediate instars and the subsequent yellow-white-black pattern of mature larvae are distinctive. Larvae often assume a characteristic curled or snaky posture when resting. Presence on dogwood species (Cornus spp.) provides a strong habitat clue. Adults resemble small wasps but lack the constricted waist of many wasps and have sawfly-typical antennae.

Adults are small, wasp-like insects with typical sawfly morphology. Larvae undergo striking color changes through development: newly hatched larvae are translucent yellowish, resembling gummy worms; intermediate instars develop a dense, snowy-white waxy coating that gives a fluffy, bird-dropping-like appearance; mature larvae shed this wax and display a bold pattern of yellow, white, and black. Larvae have six or more pairs of fleshy prolegs on abdominal segments (distinguishing them from caterpillars, which have five or fewer pairs).

Eastern North America. Documented from the northeastern United States through the mid-Atlantic region, with records from Maryland, Virginia, and surrounding areas.

Adults active from May through July. Larvae present and feeding through summer months. Mature larvae seek overwintering sites in wood during autumn before leaf drop. Winter spent as larvae in wood chambers; pupation occurs in spring.

Larvae feed on leaves of dogwood species (Cornus spp.), including grey dogwood (Cornus racemosa), silky dogwood (Cornus amomum), and flowering dogwood (Cornus florida). Early instars skeletonize leaves in groups; later instars consume entire leaves except the midvein.

• Cornus racemosa - primary hostgrey dogwood
• Cornus amomum - hostsilky dogwood
• Cornus florida - hostflowering dogwood

Females deposit eggs in clutches of 100 or more on undersides of dogwood leaves. Eggs hatch and larvae develop through summer, passing through multiple instars with dramatic appearance changes. With approach of autumn, mature larvae leave host trees and bore into rotting wood or structural wood (including decks and siding) to construct overwintering chambers. Winter is spent as larvae in these chambers. Pupation occurs in spring, with adults emerging from May through July.

Larvae initially feed gregariously, skeletonizing leaves in groups. As they grow, they become more solitary and consume entire leaves. Mature larvae exhibit wandering behavior in autumn to locate suitable wood for overwintering chamber construction. When disturbed, larvae may assume a characteristic curled or snaky posture. The white waxy coating of intermediate instars is thought to provide protection against predators and parasitoids, possibly by mimicking bird droppings or creating a physical barrier.

Herbivore and defoliator of dogwood species. Serves as prey for various predators and parasitoids. The unusual wood-boring overwintering behavior creates small galleries that may contribute to wood decomposition processes.

Occasional pest of ornamental dogwoods in landscapes and gardens. Mature larvae may damage wooden structures (decks, siding) when constructing overwintering chambers, producing small pock marks and sawdust piles. Not a significant economic pest but may cause aesthetic damage to host plants.

• Eriocampa juglandisbutternut woollyworm, another waxy-coated sawfly larva; distinguished by host association with walnut and hickory (Juglans, Carya) rather than dogwood, and by pupal overwintering in soil rather than larval overwintering in wood
• caterpillars (Lepidoptera larvae)similar larval form but distinguished by having five or fewer pairs of prolegs versus six or more in sawflies

• BugGuide
• iNaturalist taxon
• NCBI Taxonomy
• Archive — Bug of the Week
• From the Bug of the Week Mailbag: Who’s been munching on my deck? Dogwood sawfly, Macremphytus tarsatus — Bug of the Week
• What lies beneath the wax? A duo of leaf-eating sawflies: Dogwood sawfly, Macremphytus tarsatus, and Butternut woollyworm, Eriocampa juglandis — Bug of the Week