Trachelus

Jurine, 1807

stem sawflies

Trachelus is a of in the . are internal feeders in grass stems, with several species recognized as significant agricultural pests of wheat and barley. The genus occurs across the Palearctic region, with documented species in Europe, the Middle East, and Central Asia. Larval development occurs entirely within stems, causing characteristic damage often called 'whiteheads' in cereal .

Black grain-stem sawfly of Europe in the United States (1920) (19764669343) by Internet Archive Book Images. Used under a No restrictions license.

Pronunciation

How to pronounce Trachelus: /ˈtrækiːləs/

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

Identification to level requires examination of male , specifically the structure of the preapical and the hypopygium. Females can be distinguished by , including the size of denticles and the length of 3 of the ovipositor . Genetic analysis of mitochondrial (COI, cyt b) and nuclear (EF-1α) markers supports species boundaries where morphology is ambiguous.

Images

Habitat

Grassland and agricultural environments; develop internally within stems of grasses (Poaceae). Documented in arid cereal-growing regions including the Negev Desert and Mediterranean climates.

Distribution

Palearctic region. Documented from: southern Israel (Negev); southeastern and central Anatolia, Türkiye; Europe. GBIF records indicate presence in Norway and Sweden.

Seasonality

in late winter to early spring (February–March in Israel, timing varies by latitude). Larval development in spring, with in cut stem stubs during dry summer conditions. occurs in late winter prior to adult emergence. One per year.

Diet

Larval feeding on internal parenchyma of grass stems. No feeding documented.

Host Associations

Triticum aestivum - larval wheat; major agricultural pest
Hordeum vulgare - larval barley; major agricultural pest
Avena sp. - larval wild oat
Stipa holosericea - larval feather grass; first record of Stipa as

Life Cycle

deposited in young developing grass stems. feed internally, completing development within the stem. Mature larvae cut the stem internally, causing the upper portion to die (whitehead ). Larvae enter in cut stem stubs. occurs within stubs. emerge following winter rains or spring warming.

Behavior

are active for a brief period following winter rains or spring warming. Males emerge 4–6 days before females and are less numerous. Adults do not feed. are solitary .

Ecological Role

Primary consumer of grasses. Agricultural pest causing yield losses up to 55% in wheat and 50% in barley in conditions. Subject to by including Collyria coxator, Collyria calcitrator, Ceratobracon stschegolevi, and Tetrastichus sp., with rates reaching 22% in some regions.

Human Relevance

Significant pest of wheat and barley production in Mediterranean and Middle Eastern agriculture. cause direct yield loss through stem cutting. Management relies on and avoidance of broad-spectrum that harm .

Similar Taxa

Cephuscongeneric ; also stem-boring of cereals. Distinguished by genitalic and structure.
Cephus pygmaeus in same regions; is more abundant in Israeli and Turkish studies, with C. pygmaeus representing <5% of specimens in some .

More Details

Taxonomic notes

Catalogue of Life erroneously places Trachelus in (); this is a database error. The is correctly placed in : per all primary sources.

Species diversity

At least four recognized: T. flavicornis, T. libanensis, T. tabidus, and T. stipa (described 2016 from Central Anatolia). T. troglodyta mentioned as morphologically similar to T. stipa.