Siricinae

Distinguished from other Siricidae subfamilies by the presence of a pit on the hind coxa and details of antennal structure. Distinguished from other Hymenoptera by the combination of cylindrical body form, wood-boring behavior, and the long, external ovipositor. Males lack the elongated ovipositor and have more slender abdomens. Distinguished from other wood-boring insects by the wasp-like morphology and the absence of a constricted wasp waist typical of aculeate Hymenoptera.

Elongate, cylindrical body with a narrow waist. Large, powerful mandibles. Prominent, spine-like ovipositor projecting from the abdomen tip, longer in females than males. Antennae are straight and filiform. Body coloration ranges from black to metallic blue or coppery tones, often with yellow or red markings. Wings are membranous with reduced venation. Legs are stout with spines on the tibiae.

Forested and woodland areas with standing or recently dead timber. Associated with coniferous and broadleaf trees. Larvae develop within the heartwood of trees. Adults are found near host trees or on woody vegetation.

Widespread across forested regions of the Northern Hemisphere, including North America, Europe, and Asia. Presence in the Southern Hemisphere is limited to introduced species in Australia, New Zealand, and South America.

Adult emergence typically occurs in spring and summer, varying by latitude and elevation. Activity peaks when host trees are susceptible to fungal colonization.

Larvae feed on wood that has been preconditioned by symbiotic fungi (*Amylostereum* and related genera). The fungus is introduced by females during oviposition and is cultivated within the gallery. Adults do not feed; they rely on stored larval reserves.

• Amylostereum - mutualistic symbiontFemales carry fungal spores in specialized abdominal glands (mycangia) and inoculate wood during oviposition. Larvae cannot digest wood without fungal degradation.

Females bore into wood using mandibles and ovipositor, creating tunnels where eggs are laid alongside fungal inoculum. Larvae hatch and feed on the fungus-colonized wood for 1-3 years, depending on species and wood condition. Pupation occurs within the gallery. Adults emerge through exit holes, leaving characteristic round holes in timber. Some species are parthenogenetic; males are rare or absent in certain populations.

Females select host trees based on wood condition and fungal presence. Oviposition involves rhythmic drilling that can be audible. Adults are weak fliers and often found resting on bark or foliage. Males are attracted to females by pheromones. Adults do not sting or bite humans; the apparent 'stinger' is the harmless ovipositor.

Primary decomposers of dead and dying timber. Accelerate wood decay through fungal introduction and physical tunneling. Provide exit holes used by secondary cavity-nesting insects. Serve as prey for woodpeckers and parasitoid wasps.

Occasional pests of timber and processed lumber; larval tunnels degrade wood quality. Some species have been introduced outside native ranges through international timber trade, becoming invasive in plantation forests. Valued as indicators of forest health and fungal diversity. Not medically significant.

• TremicinaeOther subfamily of Siricidae; distinguished by absence of hind coxal pit and differences in antennal segment count and mycangial structure.
• XiphydriidaeAnother family of wood-boring wasps; distinguished by clubbed antennae, different wing venation, and lack of the elongated external ovipositor.
• IchneumonidaeParasitoid wasps with elongated ovipositors; distinguished by slender bodies, different wing venation, and parasitic rather than wood-boring life history.

The prominent ovipositor is often mistaken for a stinger, leading to fear of venomous stings. Siricinae cannot sting and are harmless to humans. The name 'horntail' refers to the ovipositor, not a defensive structure.

• wood-boring
• fungal symbiosis
• forest pest
• parthenogenesis
• non-stinging wasp

• BugGuide
• iNaturalist taxon