Sirex areolatus

Taxonomy

Family: Siricidae
Subfamily: Siricinae
Genus: Sirex Linnaeus, 1760
Species: Sirex areolatus (Cresson, 1868)
Common names: none

Background

Sirex areolatus is a western Nearctic species with a typical metallic blue-black coloration and completely dark legs (Schiff et al. 2012).

Diagnostic characteristics

See Sirex for genus-level diagnostic characteristics.

Females:

Males:

May be confused with

Sirex areolatus can be distinguished by the long hind tarsomere 2 and completely black legs in both sexes (Schiff et al. 2012).

Morphological and geographical variation

none recorded

Host associations

Sirex species feed on trees of Pinaceae and Cupressaceae. Sirex areolatus is recorded mainly on species of Cupressaceae such as Juniperus occidentalis (western juniper), Juniperus scopulorum (Rocky Mountain juniper), Calocedrus decurrens (incense cedar), Sequoia sempervirens (coast redwood), Thuja sp., and Taxodium distichum (bald cypress). Sirex areolatus is less commonly recorded on Pinaceae, including Pinus contorta (lodgepole pine), Pinus jeffreyi (Jeffrey pine), Pinus lambertiana (sugar pine), Pinus radiata (Monterey pine), and Pseudotsuga menziesii (Douglas 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, and in the process bore galleries through the wood (Johnson 1930, Schiff et al. 2012). It is unknown what species of fungus is harbored by the mycangia of S. areolatus; 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. areolatus is early September through early October, which is notably shorter and later than many other Sirex species in its range (Schiff et al. 2012). There is some evidence that trees with sustained damage, either from drought-related stress, weather, or other insect infestations, are preferred as hosts (Burnip et al. 2010).

A few species of parasitoid wasps have been recorded emerging from S. areolatus, including Ibalia leucospoides and Rhyssa persuasoria (Schiff et al. 2012).

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. areolatus is generally western and extends as far north as British Columbia, and south to New Mexico. This species is adventive in several eastern jurisdictions, including Nova Scotia, Virginia, Arkansas, and Florida (Schiff et al. 2012).

Map data from: GBIF.org (26 June 2019) GBIF Occurrence Download Sirex areolatus

Details about data used for maps can be found here.

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

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

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

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

Sirex areolatus tarsus; photo by H. Goulet, CNC

Sirex areolatus tarsus; photo by H. Goulet, CNC

Sirex areolatus female ovipositor base; photo by H. Goulet, CNC

Sirex areolatus female ovipositor base; photo by H. Goulet, CNC

Sirex areolatus female ovipositor apex; photo by H. Goulet, CNC

Sirex areolatus female ovipositor apex; photo by H. Goulet, CNC