Sirex cyaneus

Taxonomy

Family: Siricidae
Subfamily: Siricinae
Genus: Sirex Linnaeus, 1760
Species: Sirex cyaneus Fabricius, 1781
Common names: blue horntail

Background

Sirex cyaneus is a northeastern 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 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. The species previously identified as S. juvencus in North America has been re-classified as S. cyaneus (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.)
• 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
  small, about 0.1-0.25 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.)
• 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
  without pits or pits difficult-to-see on the basalbasal:
  towards the base; closest to the body
  half (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.)
• 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.)
• 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 black, sometimes 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
  also 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
  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 native range, Sirex cyaneus can be confused with S. nitidus and S. noctilio. The most reliable character distinguishing S. cyaneus from these species is the absence (or near absence) of pits near the basebase:
the beginning or most proximal area of any structure
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
. The European species S. torvus and S. juvencus can also be distinguished by this 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
pit character. Sirex abietinus is another similar species that occurs west of the Rocky Mountains, and it is distinguished by the 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
length (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 cyaneus is recorded on species of Pinaceae: Abies balsamea (balsam fir), Abies fraseri (Fraser fir), Abies sp., Larix sp., Picea glauca (white spruce), Picea mariana (black spruce), Pinus strobus (eastern white pine), and Pinus elliottii (slash pine). The majority of specimens reared (99%) have been on Abies spp. (spruce) (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.). The mycangia of S. cyaneus individuals harbor Amylostereum chailletii fungus (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. 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.).

Several parasitoid wasp species have been reared from S. cyaneus specimens: Ibalia leucospoides, Ibali rufipes, Rhyssa howdenorum, Rhyssa lineola 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. Several interceptions have been made in 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. cyaneus extends from Alberta to Newfoundland in the north, south to Arizona in the west, and south to North Carolina in the east (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 cyaneus

Details about data used for maps can be found here.