Orussus

Taxonomy

Family: Orussidae
Family common name: parasitic woodwasps
Subfamily: Orussinae
Genus: Orussus Latreille, 1797
Subgenera: none

Background

The Orussidae are small, predominantly black sawflies with cylindrical bodies and globular heads (Eaton and Kaufman 2007Eaton and Kaufman 2007:
Eaton ER and Kaufman K. 2007. Kaufman Field Guide to Insects of North America (Kaufman Field Guides). Houghton Mifflin Harcourt. 391 pp.). They are distinctive because they are the only sawfly family that is parasitic instead of phytophagousphytophagous:
feeding on plants
(Furniss and Carolin 1977Furniss and Carolin 1977:
Furniss RL and Carolin VM. 1977. Western forest insects. United States Deptartment of Agriculture Forest Service Miscellaneous Publication 1339: 1-655.). Current Hymenoptera phylogenies suggest that the Orussidae are the most closely related extantextant:
in existence; opposite of extinct
sawfly family to the suborder Apocrita, and specifically parasitic wasps (Vilhelmsen 2004Vilhelmsen 2004:
Vilhelmsen L. 2004. The old wasp and the tree: fossils, phylogeny, and biogeography in the Orussidae (Insecta, Hymenoptera). Biological Journal of the Linnaen Society 82: 139-160.).

Orussus are 5–14 mm in length (Furniss and Carolin 1977Furniss and Carolin 1977:
Furniss RL and Carolin VM. 1977. Western forest insects. United States Deptartment of Agriculture Forest Service Miscellaneous Publication 1339: 1-655.). They share several remarkable morphological characters with other Orussidae, including antennal insertions located extremely low on the face, reduced wing venationvenation:
the network of veins on a wing
, and a relatively long and thin 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
(Vilhelmsen et al. 2014Vilhelmsen et al. 2014:
Vilhelmsen L, Blank SM, Liu Z, and Smith DR. 2014. Discovery of a new species confirms Oriental origin of Orussus Latrielle (Hymenoptera: Orussidae). Insect Systematics and Evolution 45: 51-91. https://doi.org/10.1163/1876312X-00002087). Though it is the most speciosespeciose:
describing a taxon that includes a high number of species
and widespread of the family, collections of this genus are uncommon (Vilhelmsen et al. 2014Vilhelmsen et al. 2014:
Vilhelmsen L, Blank SM, Liu Z, and Smith DR. 2014. Discovery of a new species confirms Oriental origin of Orussus Latrielle (Hymenoptera: Orussidae). Insect Systematics and Evolution 45: 51-91. https://doi.org/10.1163/1876312X-00002087).

Diversity

Worldwide, there are 28 extantextant:
in existence; opposite of extinct
described species (Choi et al. 2014Choi et al. 2014:
Choi JK, Wei M, Vilhelmsen L, and Lee JW. 2014. A new Orusses species from South Korea, and a key to the East Asian Orussidae (Hymenoptera). Zootaxa 3873 (3): 250-258. https://doi.org/10.11646/zootaxa.3873.3.4). The lowest diversity is in the Southern Hemisphere, with only six species recorded from the NeotropicalNeotropical:
Describing the region of the Western Hemisphere that is tropical, ie. between 30°N and 30°S of the equator; includes southern Mexico, Central America, the Caribbean and South America
, African, and Australasian regions (Vilhelmsen et al. 2014Vilhelmsen et al. 2014:
Vilhelmsen L, Blank SM, Liu Z, and Smith DR. 2014. Discovery of a new species confirms Oriental origin of Orussus Latrielle (Hymenoptera: Orussidae). Insect Systematics and Evolution 45: 51-91. https://doi.org/10.1163/1876312X-00002087). Five species occur in North America (Middlekauff 1983Middlekauff 1983:
Middlekauff WW. 1983. A revision of the sawfly family Orussidae for North and Central America (Hymenoptera: Symphyta, Orussidae). University of California Publications in Entomology 101: 1-46.).

A key to North and Central American species of Orussus is included in Middlekauff 1983Middlekauff 1983:
Middlekauff WW. 1983. A revision of the sawfly family Orussidae for North and Central America (Hymenoptera: Symphyta, Orussidae). University of California Publications in Entomology 101: 1-46..

Diagnostic characteristics

• antennae low on face; antennal insertion located on ventralventral:
  of or on the underside of the body or structure
  portion of head, below the eyes and apparently below the clypeusclypeus:
  sclerotized area on the front of the head located between the antennal insertions and labrum
  (Middlekauff 1983Middlekauff 1983:
  Middlekauff WW. 1983. A revision of the sawfly family Orussidae for North and Central America (Hymenoptera: Symphyta, Orussidae). University of California Publications in Entomology 101: 1-46.)
• antennae 11-segmented in the male, 10-segmented in the female (Middlekauff 1983Middlekauff 1983:
  Middlekauff WW. 1983. A revision of the sawfly family Orussidae for North and Central America (Hymenoptera: Symphyta, Orussidae). University of California Publications in Entomology 101: 1-46.)
• female: when exposed, 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
  longer than body length and thread-like; when withdrawn, 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
  hidden inside the body, sometimes coiled (Middlekauff 1983Middlekauff 1983:
  Middlekauff WW. 1983. A revision of the sawfly family Orussidae for North and Central America (Hymenoptera: Symphyta, Orussidae). University of California Publications in Entomology 101: 1-46.)
• venation venation:
  the network of veins on a wing
  reduced in fore wingfore wing:
  the anterior wing of each pair of wings; usually the largest wing of the pair
  ; distaldistal:
  furthest from the body, opposite of proximal
  ends of veins fading to almost invisible lines (Middlekauff 1983Middlekauff 1983:
  Middlekauff WW. 1983. A revision of the sawfly family Orussidae for North and Central America (Hymenoptera: Symphyta, Orussidae). University of California Publications in Entomology 101: 1-46.)
• first flagellomereflagellomere:
  A segment of the flagellum of the antenna
  as long as combined length of the third and fourth (Goulet 1992Goulet 1992:
  Goulet H. 1992. The genera and subgenera of the sawflies of Canada and Alaska: Hymenoptera. Symphyta. The insects and arachnids of Canada. Part 20. Agriculture Canada Publication.)
• vein vein:
  a tube-like, often darkened, structure on the wings
  M of fore wingfore wing:
  the anterior wing of each pair of wings; usually the largest wing of the pair
  does not reach veinvein:
  a tube-like, often darkened, structure on the wings
  R but; veinvein:
  a tube-like, often darkened, structure on the wings
  M longer than veinvein:
  a tube-like, often darkened, structure on the wings
  1m-cu (Goulet 1992Goulet 1992:
  Goulet H. 1992. The genera and subgenera of the sawflies of Canada and Alaska: Hymenoptera. Symphyta. The insects and arachnids of Canada. Part 20. Agriculture Canada Publication.)
• mesoscutellum mesoscutellum:
  the anterior section of the scutellum
  coming to a sharp angle at apexapex:
  the end or most distal area of any structure
  (Middlekauff 1983Middlekauff 1983:
  Middlekauff WW. 1983. A revision of the sawfly family Orussidae for North and Central America (Hymenoptera: Symphyta, Orussidae). University of California Publications in Entomology 101: 1-46.)

May be confused with

Orussidae are morphologically distinct among sawfly families because of the body shape and location of 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
on head. Orussus, however, is easily confused with other genera of the family. It can be distinguished by a lack of longitudinal carinaecarina:
a ridge or raised edge
on the face between the compound eyes, lack of swelling on the hind femorafemur:
the third segment of the leg between the trochanter and the tibia
, and the shield-shaped mesoscutellummesoscutellum:
the anterior section of the scutellum
(Middlekauff 1983Middlekauff 1983:
Middlekauff WW. 1983. A revision of the sawfly family Orussidae for North and Central America (Hymenoptera: Symphyta, Orussidae). University of California Publications in Entomology 101: 1-46.).

Exotic pest species of concern

none

Host associations

In North America, Orussus are parasitoids that feed on wood-boring beetles of Buprestidae (Vilhelmsen et al. 2014Vilhelmsen et al. 2014:
Vilhelmsen L, Blank SM, Liu Z, and Smith DR. 2014. Discovery of a new species confirms Oriental origin of Orussus Latrielle (Hymenoptera: Orussidae). Insect Systematics and Evolution 45: 51-91. https://doi.org/10.1163/1876312X-00002087). Species used as host include Buprestis aurulenta, Buprestis confluenta, Buprestis laeviventris, Buprestis rufipes, Chrysophana placida, Dicera divaricate and Polycesta californica (Middlekauff 1983Middlekauff 1983:
Middlekauff WW. 1983. A revision of the sawfly family Orussidae for North and Central America (Hymenoptera: Symphyta, Orussidae). University of California Publications in Entomology 101: 1-46.).

The recorded “host” trees of North American Orussus, which are more likely to be the hosts of parasitized beetles, include Abies concolor (white fir), Abies magnifica (red fir), Acer rubrum (red maple), Acer saccharum (sugar maple), Acer macrophyllum (big leaf maple), Alnus sp. (alder), Betula occidentalis (water birch), Carya sp. (hickory), Fraxinus sp. (ash), Larix laricina (tamarack), Malus pumila (apple), Picea sitchensis (Sitka spruce), Pinus contorta (lodgepole pine), Pinus jeffreyi (Jeffrey pine), Pinus monticola (western white pine), Pinus ponderosa (ponderosa pine), Pseudotsuga menziesii (Douglas fir), Populus fremontii (Fremont cottonwood), Populus tremuloides (quaking aspen), Quercus californicus (California black oak), Tilia americanum (basswood) and Ulmus americanus (American elm) (Middlekauff 1983Middlekauff 1983:
Middlekauff WW. 1983. A revision of the sawfly family Orussidae for North and Central America (Hymenoptera: Symphyta, Orussidae). University of California Publications in Entomology 101: 1-46.).

Life history

To find a suitable oviposition site, Orussus females run up and down fallen or standing dead or damaged tree trunks, using their 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
to tap repetitively on the log. The behavior of running up and down, with the wings folded and effectively hidden, superficially resembles the behavior of carpenter ants. In the field, these females have been observed spending up to 27 minutes on the same log patrolling for an oviposition site. Whether they are able to sense a host presence in the log by chemical signals or by vibrations caused by the tapping of 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
is unclear (Powell and Turner 1975Powell and Turner 1975:
Powell JA and Turner WJ. 1975. Observations on oviposition behavior and host selection in Orussus occidentalis (Hymenoptera: Siricoidea). Journal of the Kansas Entomological Society 48 (3): 299-307.).

Females oviposit into an established, frass-filled gallery, 5–15 cm away from a wood-boring insect larvalarva:
the immature stage of holometabolous insects
. After hatching, the Orussus larvalarva:
the immature stage of holometabolous insects
moves down the mine, sometimes feeding on frassfrass:
solid larval excrement
, before beginning to feed as an external parasitoid on the wood-borer (Middlekauff 1983Middlekauff 1983:
Middlekauff WW. 1983. A revision of the sawfly family Orussidae for North and Central America (Hymenoptera: Symphyta, Orussidae). University of California Publications in Entomology 101: 1-46.). LarvaeLarva:
the immature stage of holometabolous insects
are white, legless, and grub-like. The body is slightly flattened and tapers on either end (Vilhelmsen et al. 2014Vilhelmsen et al. 2014:
Vilhelmsen L, Blank SM, Liu Z, and Smith DR. 2014. Discovery of a new species confirms Oriental origin of Orussus Latrielle (Hymenoptera: Orussidae). Insect Systematics and Evolution 45: 51-91. https://doi.org/10.1163/1876312X-00002087).

Distribution

World: Representatives of Orussus are present in Europe, North America, Southwest, East and Southeast Asia, tropical Africa, the Philippines, and New Guinea (Middlekauff 1983Middlekauff 1983:
Middlekauff WW. 1983. A revision of the sawfly family Orussidae for North and Central America (Hymenoptera: Symphyta, Orussidae). University of California Publications in Entomology 101: 1-46.)

North America: The species of Orussus in North America are mostly recorded from two distinct ranges, east and west - there are very few records for the plains states and provinces. The eastern range spans from Quebec and New England, south to Louisiana, and as far west as Ohio and Illinois. The western range includes British Columbia south to California, as far east as Ontario in the north, and some collections as far east as New Mexico in the south (Middlekauff 1983Middlekauff 1983:
Middlekauff WW. 1983. A revision of the sawfly family Orussidae for North and Central America (Hymenoptera: Symphyta, Orussidae). University of California Publications in Entomology 101: 1-46.).

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

Details about data used for maps can be found here.