Cimbicidae

The combination of large body size and distinctly clubbed antennae separates adults from other sawfly families. Larvae are distinguished from Lepidoptera caterpillars by possessing seven pairs of prolegs rather than five or fewer. The rough, pebbly skin texture and defensive coiling behavior when disturbed are additional larval characteristics. Adults may be mistaken for bees due to their plump, hairy appearance, but lack the narrow waist of Apocrita wasps.

Found in diverse environments including deciduous and mixed forests, meadows, and riparian areas with host trees. Larvae are associated with woody plants including elm, willow, birch, poplar, alder, maple, and basswood. Adults are often observed in open areas such as meadows where males may defend territories.

Widespread in the Northern Hemisphere. Documented from North America (including U.S., Canada, and Alaska), Europe, and Asia. North American records span from the Atlantic seaboard to the Rocky Mountains and Pacific coast states. Specific distribution varies by species; Cimbex americana occurs across much of North America, while Cimbex femoratus is found in Europe.

Adult activity typically occurs in late spring through summer, with observations from May through August in various regions. Larval development occurs primarily between June and October, with timing varying by latitude and elevation. One generation per year; larvae overwinter in cocoons and pupate the following spring.

Larvae are solitary herbivores feeding on leaves of deciduous trees and shrubs. Documented hosts include elm (Ulmus), willow (Salix), birch (Betula), poplar (Populus), alder (Alnus), maple (Acer), and basswood/linden (Tilia). Adults feed on sap by stripping bark from twigs, sometimes girdling them; they do not feed on pollen, nectar, or prey.

• Ulmus (elm) - larval food plantPrimary host for Cimbex americana, though not exclusive
• Salix (willow) - larval food plantMajor host for Cimbex americana
• Betula (birch) - larval food plantHost for Cimbex americana and Cimbex femoratus in Europe
• Populus (poplar) - larval food plantDocumented host for Cimbex americana
• Alnus (alder) - larval food plantDocumented host for Cimbex americana
• Acer (maple) - larval food plantOccasional host for Cimbex americana
• Tilia (basswood/linden) - larval food plantOccasional host for Cimbex americana

Complete metamorphosis with one generation per year. Females insert eggs into leaves using a saw-like ovipositor. Larvae feed solitarily on foliage, then crawl to the ground to spin tough, papery cocoons in leaf litter or shallow soil. Larvae overwinter in cocoons, pupating the following spring. Adults emerge and mate; males may defend territories in meadows.

Larvae coil when disturbed and rest in coiled positions; they can release volatile defensive chemicals from thoracic glands if threatened. Adults are sexually dimorphic in some species. Males of some species engage in aerial territorial disputes and may return to the same perch after being disturbed. Adults do not sting despite their intimidating appearance.

Herbivores that contribute to nutrient cycling through leaf consumption and subsequent deposition of frass. Larvae serve as prey for various parasitoids including egg parasites (Trichogramma minutum), larval parasites (Opheltes glaucopterus barberi), and pupal parasites (Boettcheria cimbicis). Adults may influence tree health through bark-stripping behavior that occasionally girdles twigs.

Generally considered benign; rarely causes significant defoliation of shade trees. Occasionally reported as a minor pest of elm, particularly in the northern Midwest, but populations typically do not reach damaging levels. Larvae are sometimes encountered by gardeners and naturalists; their large size and unusual appearance generate interest. Adults may be mistaken for stinging wasps or bees due to their size and appearance, causing unnecessary concern.

• Tenthredinidae (common sawflies)Lack the distinctly clubbed antennae of Cimbicidae; generally smaller body size
• Argidae (argid sawflies)Antennae not clubbed; different larval morphology and behavior
• Apidae (bees)Cimbicidae adults resemble bees in plump, hairy appearance, but lack the constricted waist (petiole) of Apocrita; also lack pollen-collecting structures
• Vespidae (wasps)Cimbicidae lack the narrow waist and stinger of vespid wasps; have clubbed antennae not found in this family
• Lepidoptera caterpillarsSawfly larvae resemble caterpillars but possess seven pairs of prolegs versus five or fewer in Lepidoptera; also have rough, pebbly skin texture distinct from most caterpillars

Despite their wasp-like appearance and common name 'sawfly,' adults do not sting and are harmless to humans. The name 'sawfly' refers to the saw-like ovipositor used for egg-laying, not to any defensive capability. Their large size and robust build often lead to misidentification as dangerous wasps or hornets.

• sawfly
• Symphyta
• herbivore
• clubbed antennae
• large size
• solitary larva
• defensive coiling
• non-stinging
• deciduous forest
• Northern Hemisphere

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Cimbicidae | Beetles In The Bush
• Bug Eric: Emerald Valley, 2016
• Bug Eric: Wasp Wednesday: Elm Sawfly