Sirex noctilio (Fabricius, 1793)

Like many hymenopterans this species is haplodiploid. Unfertilized eggs produce male offspring (haploid) and fertilized eggs produce female offspring (diploid).
Females use a long, wood boring ovipositor at the terminus of their abdomen to drill into host trees. Symbiotic fungal spores of Amylostereum areolatum, a white-rot basidiomycete, are injected into host trees. Females also inject a phytotoxic mucus and eggs via their ovipositor. Preliminary drills are conducted into host trees to assess wood conditions and inject mucus & fungal spores prior to egg deposition. The mucus kills the tree conditioning it for the symbiotic fungus, which developing larvae will feed upon as they bore through the wood. Egg eclosion can take 8-64 days and is highly dependent on temperature. Once the eggs have hatched, larvae bore through the wood and develop for the next year entering diapause during winter months. Small subsets of populations have shown a 2-year life-cycle and others have shown shortened, 3-month development.
Males emerge prior to females and sex ratios are generally skewed toward males with a 3:1 ratio, some have been greater.

Sirex longicauda (Middlekauff)
- Native to the U.S., its current distribution throughout CA, CO, ID, MT, NV, NM, OR, and UT. There are records of occurence in eastern states, but these were probably from infested wood from the west

Sirex areolatus (Cresson)
- Native to the U.S. current distribution includes most of the western states and Canadian provinces.

Fungus / infection vector
conidium of Amylostereum areolatum is spread by mycangial pouches of female of Sirex noctilio

Fungus / feeder
larva of Sirex noctilio feeds on wood rot imperfect state of Amylostereum areolatum