Sirex torvus

Taxonomy

Family: Siricidae
Subfamily: Siricinae
Genus: Sirex Linnaeus, 1760
Species: Sirex torvus Harris, 1779
Common names: none

Background

Sirex torvus is a PalearcticPalearctic:
describing the region of the northern hemisphere that includes Europe, Asia south to the Himalayas and northern Africa
species with a typical metallic blue-black coloration and red 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.).

The European species previously identified as S. cyaneus has, through morphological and molecular analysis, been determined to be a separate species, and is now classified as S. torvus. Sirex cyaneus occurs in North America (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
  reddish-brown (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.)
• antennae 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
  light reddish-brown (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.)
• 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
  extremely small, <0.25 times size of laterallateral:
  of or towards the side of the body
  ocellus (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.)
• 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 2–10 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
  2–3.6 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 with raised margins forming a net-like pattern (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
  0.8 times 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.)
• apical apical:
  towards the apex; farthest away from the body
  portion of the 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 longer than basalbasal:
  towards the base; closest to the body
  portion (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:

• hind femurfemur:
  the third segment of the leg between the trochanter and the tibia
  completely reddish-brown (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.)
• mid and hind tibiatibia:
  the fourth segment of the leg, between the femur and the tarsus
  usually with narrow band of reddish-brown at basebase:
  the beginning or most proximal area of any structure
  , remainder 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.)
• mid tarsomeres 1–3 black
• mesoscutum mesoscutum:
  the central and dorsal portion of the thorax between the scutellum and postnotum
  pits with projections, margins forming a net-like pattern (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.)
• apical apical:
  towards the apex; farthest away from the body
  tergite and cornuscornus:
  a pointed horn-like process on the apical end of the abdomen in Siricidae sawflies; on tergite 10 in females, sternite 9 in males
  reddish-brown (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 generally 1–3 diameters apart posterodorsallyposterodorsal:
  describes location towards the back on the uppererside of the body; posterior and dorsal
  (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.)
• setae behind compound eye each with a deep pit 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.)

May be confused with

In its range, S. torvus can be distinguished from S. juvencus and S. noctilio by the short 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
, dark antennaeantenna:
the sensory organ emerging from the front of the head, usually between the compound eyes and above the clypeus; includes the flagellum, scape and pedicel
, and the completely light-colored tarsitarsus:
the fifth and last segment of the leg
(Benson 1943Benson 1943:
Benson RB. 1943. Studies in Siricidae, especially of Europe and southern Asia (Hymenoptera, Smphyta). Bulletin of Entomological Research 34 (1): 27-51. https://doi.org/10.1017/S0007485300023464). Previously considered to be the same species, S. cyaneus is differentiated from S. torvus by the lack of pits on the basalbasal:
towards the base; closest to the body
part of the 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
and the shorter length of the 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
(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 torvus is recorded from species of Pinaceae including Abies procera (noble fir), Abies alba (silver fir), Pinus sylvestris (Scots pine), Pinus spp., Larix europaea (European larch), Larix spp., and Picea spp. (spruce) (Smith 1978Smith 1978:
Smith DR. 1978. Suborder Symphyta (Xyelidae, Parachexyelidae, Parapamphiliidae, Xyelydidae, Karatavitidae, Gigasiricidae, Sepulcidae, Pseudosiricidae, Anaxyelidae, Siricidae, Xiphydriidae, Paroryssidae, Xyelotomidae, Blasticotomidae, Pergidae). Hymenopterorum Catalogus 14: 1-193.).

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.).

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. cyaneus is early July through early September, with most collections in early August (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.).

The specific biology of S. torvus is not known.

Distribution

World: Sirex torvus occurs in most of Europe, as far north as Sweden, east to Germany, and west to the British Isles (Smith 1978Smith 1978:
Smith DR. 1978. Suborder Symphyta (Xyelidae, Parachexyelidae, Parapamphiliidae, Xyelydidae, Karatavitidae, Gigasiricidae, Sepulcidae, Pseudosiricidae, Anaxyelidae, Siricidae, Xiphydriidae, Paroryssidae, Xyelotomidae, Blasticotomidae, Pergidae). Hymenopterorum Catalogus 14: 1-193.).

North America: not recorded

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

Details about data used for maps can be found here.

Sirex cyaneus for many years was considered a HolarcticHolarctic:
describing the region of the Northern Hemisphere that includes both the Nearctic and Palearctic regions
species. Recent research determined that European specimens of S. cyaneus are a different species, and these specimens have been named S. torvus. See 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. about this designation.