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 NearcticNearctic:
describing the region of the Northern Hemisphere that includes North America south through northern Mexico
species with a typical metallic blue-black coloration and completely dark legs (Schiff et al. 2012Schiff et al. 2012:
Schiff NM, Goulet H, Smith DR, Boudreault C, Wilson AD, and Scheffler BE. 2012. Siricidae (Hymenoptera: Symphyta: Siricoidea) of the Western Hemisphere. Canadian Journal of Arthropod Identification 21: 1-305.).

Diagnostic characteristics

See Sirex for genus-level diagnostic characteristics.

Females:

• hind femurfemur:
  the third segment of the leg between the trochanter and the tibia
  black (Schiff et al. 2012Schiff et al. 2012:
  Schiff NM, Goulet H, Smith DR, Boudreault C, Wilson AD, and Scheffler BE. 2012. Siricidae (Hymenoptera: Symphyta: Siricoidea) of the Western Hemisphere. Canadian Journal of Arthropod Identification 21: 1-305.)
• abdomen abdomen:
  the third and last segment of an insect's body; in sawflies this is usually made up of 11 segments (segments 9 and 10 often fused)
  metallic blue-black (Schiff et al. 2012Schiff et al. 2012:
  Schiff NM, Goulet H, Smith DR, Boudreault C, Wilson AD, and Scheffler BE. 2012. Siricidae (Hymenoptera: Symphyta: Siricoidea) of the Western Hemisphere. Canadian Journal of Arthropod Identification 21: 1-305.)
• all tibiaetibia:
  the fourth segment of the leg, between the femur and the tarsus
  and tarsitarsus:
  the fifth and last segment of the leg
  dark brown or black (Schiff et al. 2012Schiff et al. 2012:
  Schiff NM, Goulet H, Smith DR, Boudreault C, Wilson AD, and Scheffler BE. 2012. Siricidae (Hymenoptera: Symphyta: Siricoidea) of the Western Hemisphere. Canadian Journal of Arthropod Identification 21: 1-305.)
• fore wing fore wing:
  the anterior wing of each pair of wings; usually the largest wing of the pair
  vein 3A present
• pits on the vertexvertex:
  the dorsal portion of the head between the compound eyes, between the occiput and frons
  and genagena:
  the area of the head between the compound eye and clypeus; also called the cheek
  scattered, about 1–5 pit diameters apart (Schiff et al. 2012Schiff et al. 2012:
  Schiff NM, Goulet H, Smith DR, Boudreault C, Wilson AD, and Scheffler BE. 2012. Siricidae (Hymenoptera: Symphyta: Siricoidea) of the Western Hemisphere. Canadian Journal of Arthropod Identification 21: 1-305.)
• second hind tarsomeretarsomere:
  a segment of the tarsus
  5 times as long as wide (Schiff et al. 2012Schiff et al. 2012:
  Schiff NM, Goulet H, Smith DR, Boudreault C, Wilson AD, and Scheffler BE. 2012. Siricidae (Hymenoptera: Symphyta: Siricoidea) of the Western Hemisphere. Canadian Journal of Arthropod Identification 21: 1-305.)
• mesoscutum mesoscutum:
  the central and dorsal portion of the thorax between the scutellum and postnotum
  pits dense, forming a few transverse ridges (Schiff et al. 2012Schiff et al. 2012:
  Schiff NM, Goulet H, Smith DR, Boudreault C, Wilson AD, and Scheffler BE. 2012. Siricidae (Hymenoptera: Symphyta: Siricoidea) of the Western Hemisphere. Canadian Journal of Arthropod Identification 21: 1-305.)
• ovipositor ovipositor:
  the female organ that deposits eggs and is used to drill into plant tissue, located at the apex of the abdomen, made up of the lance and lancet
  with clear pits at the basebase:
  the beginning or most proximal area of any structure
  (Schiff et al. 2012Schiff et al. 2012:
  Schiff NM, Goulet H, Smith DR, Boudreault C, Wilson AD, and Scheffler BE. 2012. Siricidae (Hymenoptera: Symphyta: Siricoidea) of the Western Hemisphere. Canadian Journal of Arthropod Identification 21: 1-305.)
• second hind tarsomeretarsomere:
  a segment of the tarsus
  with pulvilluspulvillus:
  soft pads used for surface adhesion, located in sawflies on the first 4 segments of the tarsus
  0.35–0.5 times the length of tarsomeretarsomere:
  a segment of the tarsus
  (Schiff et al. 2012Schiff et al. 2012:
  Schiff NM, Goulet H, Smith DR, Boudreault C, Wilson AD, and Scheffler BE. 2012. Siricidae (Hymenoptera: Symphyta: Siricoidea) of the Western Hemisphere. Canadian Journal of Arthropod Identification 21: 1-305.)
• basal basal:
  towards the base; closest to the body
  section of ovipositorovipositor:
  the female organ that deposits eggs and is used to drill into plant tissue, located at the apex of the abdomen, made up of the lance and lancet
  sheath length about 0.6–1 times the length of apicalapical:
  towards the apex; farthest away from the body
  section (Schiff et al. 2012Schiff et al. 2012:
  Schiff NM, Goulet H, Smith DR, Boudreault C, Wilson AD, and Scheffler BE. 2012. Siricidae (Hymenoptera: Symphyta: Siricoidea) of the Western Hemisphere. Canadian Journal of Arthropod Identification 21: 1-305.)

Males:

• all legs completely black (Schiff et al. 2012Schiff et al. 2012:
  Schiff NM, Goulet H, Smith DR, Boudreault C, Wilson AD, and Scheffler BE. 2012. Siricidae (Hymenoptera: Symphyta: Siricoidea) of the Western Hemisphere. Canadian Journal of Arthropod Identification 21: 1-305.)
• gena gena:
  the area of the head between the compound eye and clypeus; also called the cheek
  dark blue with metallic reflections (Schiff et al. 2012Schiff et al. 2012:
  Schiff NM, Goulet H, Smith DR, Boudreault C, Wilson AD, and Scheffler BE. 2012. Siricidae (Hymenoptera: Symphyta: Siricoidea) of the Western Hemisphere. Canadian Journal of Arthropod Identification 21: 1-305.)
• gena gena:
  the area of the head between the compound eye and clypeus; also called the cheek
  pits scattered and somewhat large (Schiff et al. 2012Schiff et al. 2012:
  Schiff NM, Goulet H, Smith DR, Boudreault C, Wilson AD, and Scheffler BE. 2012. Siricidae (Hymenoptera: Symphyta: Siricoidea) of the Western Hemisphere. Canadian Journal of Arthropod Identification 21: 1-305.)

May be confused with

Sirex areolatus can be distinguished by the long hind tarsomeretarsomere:
a segment of the tarsus
2 and completely black legs in both sexes (Schiff et al. 2012Schiff et al. 2012:
Schiff NM, Goulet H, Smith DR, Boudreault C, Wilson AD, and Scheffler BE. 2012. Siricidae (Hymenoptera: Symphyta: Siricoidea) of the Western Hemisphere. Canadian Journal of Arthropod Identification 21: 1-305.).

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. 2012Schiff et al. 2012:
Schiff NM, Goulet H, Smith DR, Boudreault C, Wilson AD, and Scheffler BE. 2012. Siricidae (Hymenoptera: Symphyta: Siricoidea) of the Western Hemisphere. Canadian Journal of Arthropod Identification 21: 1-305.).

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. LarvaeLarva:
the immature stage of holometabolous insects
feed on the fungus, and in the process bore galleries through the wood (Johnson 1930Johnson 1930:
Johnson CW. 1930. On the variation and abundance of Sirex nitidus Harris. Psyche 37 (3): 281-282. https://doi.org/10.1155/1930/62786, Schiff et al. 2012Schiff et al. 2012:
Schiff NM, Goulet H, Smith DR, Boudreault C, Wilson AD, and Scheffler BE. 2012. Siricidae (Hymenoptera: Symphyta: Siricoidea) of the Western Hemisphere. Canadian Journal of Arthropod Identification 21: 1-305.). It is unknown what species of fungus is harbored by the mycangia of S. areolatus; Amylostereum areolatum and A. chailletii are associated with other NearcticNearctic:
describing the region of the Northern Hemisphere that includes North America south through northern Mexico
Sirex (Hajek et al. 2013Hajek et al. 2013:
Hajek AE, Nielsen C, Kepler RM, Long SJ, and Castrillo L. 2013. Fidelity among Sirex woodwasps and their fungal symbionts. Microbial Ecology 65: 753-762. https://doi.org/10.1007/s00248-013-0218-z).

Larvae are creamy white and grub-like in appearance with a dark head capsule. As with adults, larvaelarva:
the immature stage of holometabolous insects
possess a short dorsaldorsal:
of or on the top surface of the body or structure
horn on the posterior end of the body. The larvaelarva:
the immature stage of holometabolous insects
bore galleries into wood, feeding until pupation and subsequent emergence. Throughout this process, the larvaelarva:
the immature stage of holometabolous insects
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 larvaelarva:
the immature stage of holometabolous insects
that develop into the mycangia after metamorphosis (Schiff et al. 2012Schiff et al. 2012:
Schiff NM, Goulet H, Smith DR, Boudreault C, Wilson AD, and Scheffler BE. 2012. Siricidae (Hymenoptera: Symphyta: Siricoidea) of the Western Hemisphere. Canadian Journal of Arthropod Identification 21: 1-305.).

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. 2012Schiff et al. 2012:
Schiff NM, Goulet H, Smith DR, Boudreault C, Wilson AD, and Scheffler BE. 2012. Siricidae (Hymenoptera: Symphyta: Siricoidea) of the Western Hemisphere. Canadian Journal of Arthropod Identification 21: 1-305.). 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. 2010Burnip et al. 2010:
Burnip GM, Voice D, and Brockerhoff EG. 2010. Interceptions and incursions of exotic Sirex species and other siricids (Hymenoptera: Siricidae). New Zealand Journal of Forestry Science 40: 133-140.).

A few species of parasitoid wasps have been recorded emerging from S. areolatus, including Ibalia leucospoides and Rhyssa persuasoria (Schiff et al. 2012Schiff et al. 2012:
Schiff NM, Goulet H, Smith DR, Boudreault C, Wilson AD, and Scheffler BE. 2012. Siricidae (Hymenoptera: Symphyta: Siricoidea) of the Western Hemisphere. Canadian Journal of Arthropod Identification 21: 1-305.).

Distribution

World: North America. This species has been intercepted at ports in England and New Zealand (Schiff et al. 2012Schiff et al. 2012:
Schiff NM, Goulet H, Smith DR, Boudreault C, Wilson AD, and Scheffler BE. 2012. Siricidae (Hymenoptera: Symphyta: Siricoidea) of the Western Hemisphere. Canadian Journal of Arthropod Identification 21: 1-305.).

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. 2012Schiff et al. 2012:
Schiff NM, Goulet H, Smith DR, Boudreault C, Wilson AD, and Scheffler BE. 2012. Siricidae (Hymenoptera: Symphyta: Siricoidea) of the Western Hemisphere. Canadian Journal of Arthropod Identification 21: 1-305.).

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

Details about data used for maps can be found here.