Tethida barda

The common name "Black-headed Ash Sawfly" refers to a dark head contrasting with a lighter body, though specific diagnostic features for field identification are not well documented in available sources. As a member of Tenthredinidae, it lacks the constricted "wasp waist" (petiole) characteristic of many other Hymenoptera. Association with ash host plants provides a contextual clue for identification.

Associated with ash trees (Fraxinus species), indicating woodland, forest edge, and urban or suburban environments where ash is present.

Recorded from eastern and central Canadian provinces: Manitoba, New Brunswick, Nova Scotia, and Ontario. The species range extends into the northeastern United States based on host plant distribution, though specific US state records are not confirmed in the provided sources.

Larvae feed on ash (Fraxinus) foliage. Adults do not feed; they rely on fat reserves accumulated during the larval stage.

• Fraxinus - larval host plantAsh trees; specific Fraxinus species not documented in available sources

Herbivore; larval feeding on ash contributes to nutrient cycling through defoliation and subsequent leaf litter. Serves as prey for parasitoids and other natural enemies, though specific associations are not documented.

Can be a minor pest of ornamental ash trees when larval populations are high, causing defoliation. Not known to be economically significant in forestry contexts.

• Other Tethida speciesCongeners may share ash host associations; specific distinguishing characters require examination of morphological details not covered in general sources.
• Other ash-feeding sawfliesSeveral Tenthredinidae larvae feed on Fraxinus; accurate identification to species typically requires adult specimens and reference to taxonomic keys.

• sawfly
• ash
• Tenthredinidae
• herbivore
• forest insect
• Nearctic

• BugGuide
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• A Honey of a Bee | Bug Squad