Sirex abietinus

Taxonomy

Family: Siricidae
Subfamily: Siricinae
Genus: Sirex Linnaeus, 1760
Species: Sirex abietinus Goulet, 2012
Common names: none

Background

Sirex abietinus is a western Nearctic species with a typical metallic blue-black coloration and mostly light-colored legs (Schiff et al. 2012).

Diagnostic characteristics

See Sirex for genus-level diagnostic characteristics.

Females:

Males:

May be confused with

Sirex abietinus females can be distinguished from S. cyaneus by the missing pits at the base of the ovipositor and the long cornus, and from S. californicus and S. nitidus by the ovipositor pit length and the relative length of the pulvillus on the second hind tarsomere. The same set of characters can distinguish S. abietinus from S. noctilio, although the two species do not currently have overlapping ranges (Schiff et al. 2012).

Morphological and geographical variation

none recorded

Host associations

Sirex species feed on trees of Pinaceae and Cupressaceae. Sirex abietinus is recorded on Pinaceae species Abies amabilis (Pacific silver fir), Abies concolor (white fir), Abies lasiocarpa (subalpine fir), Picea engelmannii (Engelmann spruce), Picea glauca (white spruce), Picea sitchensis (Sitka spruce), and Tsuga heterophylla (western hemlock). The majority of specimens reared (83%) have been on Abies spp. (fir) (Schiff et al. 2012).

Life history

Female Sirex harbor symbiotic basidiomycete fungus in abdominal glands called mycangia. During oviposition, the site is inoculated with the fungus, which begins to decompose the surrounding wood. Larvae feed on the fungus, boring galleries through the wood while they feed (Johnson 1930, Schiff et al. 2012). It is unknown what species of fungus is harbored by the mycangia of S. abietinus; Amylostereum areolatum and A. chailletii are associated with other Nearctic Sirex (Hajek et al. 2013).

Larvae are creamy white and grub-like in appearance with a dark head capsule. As with adults, larvae possess a short dorsal horn on the posterior end of the body. The larvae bore galleries into wood, feeding until pupation and subsequent emergence. Throughout this process, the larvae use their horn to pack the tunnel behind them with sawdust. Emergence holes are perfectly circular. The fungal symbiont is carried in specialized organs in female larvae that develop into the mycangia after metamorphosis (Schiff et al. 2012).

The documented flight period of S. abietinus is late July through mid-September, with most collections in August (Schiff et al. 2012). There is some evidence that preferred hosts have sustained damage from drought-related stress, weather, or other insect infestations (Burnip et al. 2010).

Distribution

World: North America. This species has been intercepted at ports in England and New Zealand (Schiff et al. 2012).

North America: The range of S. abietinus is west of the Rocky Mountains to the Pacific ocean, extending as far north as the Yukon Territory, and south to California, Utah, and Colorado (Schiff et al. 2012).

Map data from Washington State Department of Agriculture Entomology Collection.

Details about data used for maps can be found here.

Sirex abietinus female lateral habitus; photo by H. Goulet, CNC

Sirex abietinus female lateral habitus; photo by H. Goulet, CNC

Sirex abietinus female dorsal habitus; photo by J. Orr, WSDA

Sirex abietinus female dorsal habitus; photo by J. Orr, WSDA

Sirex abietinus male lateral habitus; photo by H. Goulet, CNC

Sirex abietinus male lateral habitus; photo by H. Goulet, CNC

Sirex abietinus female cornus; photo by H. Goulet, CNC

Sirex abietinus female cornus; photo by H. Goulet, CNC

Sirex abietinus ovipositor pits; photo by H. Goulet, CNC

Sirex abietinus ovipositor pits; photo by H. Goulet, CNC

Sirex abietinus ovipositor apex; photo by H. Goulet, CNC

Sirex abietinus ovipositor apex; photo by H. Goulet, CNC