Dineura

Taxonomy

Family: Tenthredinidae
Family common name: common sawflies
Subfamily: Nematinae
Tribe: Nematini
Genus: Dineura Dahlbom, 1835
Subgenera: none

Background

The Tenthredinidae are the most species-rich family and are found throughout the world, in all continents but Antarctica. They are known as the “common sawflies.” They can generally be recognized by a cylindrical body and long, segmented 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
. Otherwise, they come in a variety of colors, sizes, and forms (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.).

Nematinae is the second-largest subfamily of Tenthredinidae, with over 1,250 species (Prous et al. 2014Prous et al. 2014:
Prous M, Blank SM, Goulet H, Heibo E, Liston A, Malm T, Nyman T, Schmidt S, Smith DR, Varing;rdal H, Viitasaari M, Vikberg V, and Taeger A. 2014. The genera of Nematinae (Hymenoptera, Tenthredinidae). Journal of Hymenoptera Research 40: 1-69. " target="_blank">https://doi.org/10.3897/JHR.40.7442). They are most diverse in northern Eurasia and North America; only a few species occur in the Southern Hemisphere. Nematinae sawflies have a variety of feeding habits including external leaf feeding, leaf mining, and gall forming, and feed on a variety of hosts (Smith 2003bSmith 2003b:
Smith DR. 2003b. A Synopsis of the sawflies (Hymenoptera: Symphyta) of America south of the United States: Tenthredinidae (Nematinae, Heterarthrinae, Tenthredininae). Transactions of the American Entomological Society 129 (1): 1-45.).

The Nematinae have been subject to numerous revisions in recent years. As of 2021, there are no comprehensive keys to many of the North American species of Nematinae (Prous et al. 2014Prous et al. 2014:
Prous M, Blank SM, Goulet H, Heibo E, Liston A, Malm T, Nyman T, Schmidt S, Smith DR, Varing;rdal H, Viitasaari M, Vikberg V, and Taeger A. 2014. The genera of Nematinae (Hymenoptera, Tenthredinidae). Journal of Hymenoptera Research 40: 1-69. " target="_blank">https://doi.org/10.3897/JHR.40.7442). Because of changing taxonomy and extreme variability in morphology, identifying genera and species in the Nematinae may be more challenging than in other subfamilies of Tenthredindae. For this reason, knowing the host or behaviors of a specimen can be extremely helpful for identification within this subfamily.

Dineura is monotypicmonotypic:
describes having only one representative; ex. a genus that includes only one species
in North America. Dineura militaris is variable in color patterning, but is always black and orange and somewhat small in size (about 6–8 mm in length) (Smith 1975Smith 1975:
Smith DR. 1975. The sawfly genus Hemichroa Stephens : A review of species (Hymenoptera: Tenthredinidae). Insect Systematics and Evolution 6 (3-4): 297-302. https://doi.org/10.1163/187631275X00145).

Diversity

There are 19 described species worldwide. One species occurs in North America (Taeger et al. 2018Taeger et al. 2018:
Taeger A, Liston AD, Prous M, Groll EK, Gehroldt T, and Blank SM. 2018. ECatSymmdash;Electronic World Catalog of Symphyta (Insecta, Hymenoptera). Program version 5.0 (19 Dec 2018), data version 40 (23 Sep 2018). Senckenberg Deutsches Entomologisches Institut (SDEI), Muuml;ncheberg. https://sdei.de/ecatsym/ Accessed: 28 Jan 2020.).

Diagnostic characteristics

Subfamily characters​

• veins M and 1m-cu convergent toward the stigmastigma:
  a section of the fore wing at the apex of vein C that is sclerotized, rounded and often darkened
  (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.)
• fore wing fore wing:
  the anterior wing of each pair of wings; usually the largest wing of the pair
  vein 2m-cu meeting cellcell:
  1. a membranous area of the wing between veins, 2. a small cavity or closed space
  1Rs above (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.)

Genus characters

• mandibles symmetrical (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.)
• clypeus clypeus:
  sclerotized area on the front of the head located between the antennal insertions and labrum
  deeply emarginated (Prous et al. 2014Prous et al. 2014:
  Prous M, Blank SM, Goulet H, Heibo E, Liston A, Malm T, Nyman T, Schmidt S, Smith DR, Varing;rdal H, Viitasaari M, Vikberg V, and Taeger A. 2014. The genera of Nematinae (Hymenoptera, Tenthredinidae). Journal of Hymenoptera Research 40: 1-69. " target="_blank">https://doi.org/10.3897/JHR.40.7442)
• malar space malar space:
  the minimum distance between the base of the mandible and the ventral margin of the compound eye
  about equal to diameter of front ocellusocellus:
  a simple bead-like eye, often on the dorsum of the head in groups of 1-3
  (Prous et al. 2014Prous et al. 2014:
  Prous M, Blank SM, Goulet H, Heibo E, Liston A, Malm T, Nyman T, Schmidt S, Smith DR, Varing;rdal H, Viitasaari M, Vikberg V, and Taeger A. 2014. The genera of Nematinae (Hymenoptera, Tenthredinidae). Journal of Hymenoptera Research 40: 1-69. " target="_blank">https://doi.org/10.3897/JHR.40.7442)
• antennae long and thin, longer than 2X width of head (Smith 1975Smith 1975:
  Smith DR. 1975. The sawfly genus Hemichroa Stephens : A review of species (Hymenoptera: Tenthredinidae). Insect Systematics and Evolution 6 (3-4): 297-302. https://doi.org/10.1163/187631275X00145)
• pedicel pedicel:
  the second antennal segment, between the scape and flagellum
  wider than long (Smith 1975Smith 1975:
  Smith DR. 1975. The sawfly genus Hemichroa Stephens : A review of species (Hymenoptera: Tenthredinidae). Insect Systematics and Evolution 6 (3-4): 297-302. https://doi.org/10.1163/187631275X00145)
• third antennal segment about equal to fifth segment (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.)
• fore wing fore wing:
  the anterior wing of each pair of wings; usually the largest wing of the pair
  veins M and Rs+M relatively widely separated on veinvein:
  a tube-like, often darkened, structure on the wings
  R (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.)
• fore wing fore wing:
  the anterior wing of each pair of wings; usually the largest wing of the pair
  vein 2A+3A curved upwards and meeting 1A, though often quite faint and hard to discern (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., Smith 1975Smith 1975:
  Smith DR. 1975. The sawfly genus Hemichroa Stephens : A review of species (Hymenoptera: Tenthredinidae). Insect Systematics and Evolution 6 (3-4): 297-302. https://doi.org/10.1163/187631275X00145)
• fore wing fore wing:
  the anterior wing of each pair of wings; usually the largest wing of the pair
  vein 2r-rs absent (Smith 1975Smith 1975:
  Smith DR. 1975. The sawfly genus Hemichroa Stephens : A review of species (Hymenoptera: Tenthredinidae). Insect Systematics and Evolution 6 (3-4): 297-302. https://doi.org/10.1163/187631275X00145)
• hind wing hind wing:
  the posterior wing of each pair of wings
  vein 2A meeting 1A; basalbasal:
  towards the base; closest to the body
  anal cellanal cell:
  cell A of either the fore wing or hind wing
  present (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.)
• larger (anterior) fore tibialfore tibia:
  the tibia of the fore leg
  spur without velum (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.)
• pulvilli short; first pulvilluspulvillus:
  soft pads used for surface adhesion, located in sawflies on the first 4 segments of the tarsus
  about 1/3 the length of the tarsomeretarsomere:
  a segment of the tarsus
  (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.)
• female cercuscercus:
  structures emerging posterolaterally from the apex of the abdomen
  about 3–6X as long as wide (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.)

May be confused with

Dineura may be confused with other genera in the subfamily Nematinae — especially Hemichroa — but can be distinguished from it and most other genera that have fore wingfore wing:
the anterior wing of each pair of wings; usually the largest wing of the pair
vein 2A+3A curved upwards by the long 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
, the short pulvillipulvillus:
soft pads used for surface adhesion, located in sawflies on the first 4 segments of the tarsus
, the absence of the velum on the larger fore tibialfore tibia:
the tibia of the fore leg
spur, and the absence of fore wingfore wing:
the anterior wing of each pair of wings; usually the largest wing of the pair
vein 2r-rs (Smith 1975Smith 1975:
Smith DR. 1975. The sawfly genus Hemichroa Stephens : A review of species (Hymenoptera: Tenthredinidae). Insect Systematics and Evolution 6 (3-4): 297-302. https://doi.org/10.1163/187631275X00145, 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.).

Exotic pest species of concern

none

Host associations

Dineura militaris feeds on Amelanchier (serviceberry) (Smith 1975Smith 1975:
Smith DR. 1975. The sawfly genus Hemichroa Stephens : A review of species (Hymenoptera: Tenthredinidae). Insect Systematics and Evolution 6 (3-4): 297-302. https://doi.org/10.1163/187631275X00145).

Life history

The larvaelarva:
the immature stage of holometabolous insects
feed on the underside of the leaf. At maturity, the larvaelarva:
the immature stage of holometabolous insects
fall to the ground to pupate or overwinter in the soil. Dineura militaris is univoltineunivoltine:
describing an insect with a life cycle of one generation per year
(Smith 1975Smith 1975:
Smith DR. 1975. The sawfly genus Hemichroa Stephens : A review of species (Hymenoptera: Tenthredinidae). Insect Systematics and Evolution 6 (3-4): 297-302. https://doi.org/10.1163/187631275X00145).

Distribution

World: The genus is known from North America, throughout Europe, Russia, China, Japan, and Thailand (Taeger et al. 2018Taeger et al. 2018:
Taeger A, Liston AD, Prous M, Groll EK, Gehroldt T, and Blank SM. 2018. ECatSymmdash;Electronic World Catalog of Symphyta (Insecta, Hymenoptera). Program version 5.0 (19 Dec 2018), data version 40 (23 Sep 2018). Senckenberg Deutsches Entomologisches Institut (SDEI), Muuml;ncheberg. https://sdei.de/ecatsym/ Accessed: 28 Jan 2020.).

North America: Dineura militaris occurs throughout the northern United States and Canada, and as far north as Alaska (Smith 1975Smith 1975:
Smith DR. 1975. The sawfly genus Hemichroa Stephens : A review of species (Hymenoptera: Tenthredinidae). Insect Systematics and Evolution 6 (3-4): 297-302. https://doi.org/10.1163/187631275X00145).

Map data from: GBIF.org (29 October 2019) GBIF Occurrence Download Hemichroa

Details about data used for maps can be found here.