Kerita

Taxonomy

Family: Tenthredinidae
Family common name: common sawflies
Subfamily: Nematinae
Tribe: Pseudodineurini
Genus: Kerita Ross, 1937
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.

Kerita is a rare genus of small sawflies, about 3.5–4 mm in length. Most species are black with light yellow legs (Smith 1976bSmith 1976b:
Smith DR. 1976b. World genera of the leaf-mining sawfly tribe Fenusini (Hymenoptera: Tenthredinidae). Insect Systematics and Evolution 7: 253-260.).

Diversity

There are three described species worldwide, and all occur 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.).

A key to species is included in Smith 1976bSmith 1976b:
Smith DR. 1976b. World genera of the leaf-mining sawfly tribe Fenusini (Hymenoptera: Tenthredinidae). Insect Systematics and Evolution 7: 253-260..

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 2A+3A incomplete and straight (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)
• 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 or 2Rs above, interstitial with or very close to crossveincrossvein:
  short section of wing vein that connects two larger veins
  2r-m (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​

• body small: length about 2–5 mm (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.)
• postocular postocular:
  describes area behind the compound eye
  area without fine pits, spaces between punctures shining and smooth (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.)
• ocelli arranged in a flat triangle (Ross 1937Ross 1937:
  Ross HH. 1937. A generic classification of the Nearctic sawflies (Hymenoptera, Symphyta). University of Ilinois Bulletin 34 (94): 1-173.): middle ocellusocellus:
  a simple bead-like eye, often on the dorsum of the head in groups of 1-3
  tangential to anterioranterior:
  of or towards the front or head
  margin of laterallateral:
  of or towards the side of the body
  ocelli, space between laterallateral:
  of or towards the side of the body
  ocelli about twice as wide as middle ocellus
• notauli distinct, sharply outlined (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)
• fore wing fore wing:
  the anterior wing of each pair of wings; usually the largest wing of the pair
  2r-m sometimes absent (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)

May be confused with

Kerita may be confused with other genera in the subfamily Nematinae—especially those with fore wingfore wing:
the anterior wing of each pair of wings; usually the largest wing of the pair
vein 2r-rs present and veinvein:
a tube-like, often darkened, structure on the wings
2m-cu meeting cellcell:
1. a membranous area of the wing between veins, 2. a small cavity or closed space
2Rs—but can be distinguished from most genera by the incomplete hind winghind wing:
the posterior wing of each pair of wings
vein 2A (some species of Pristiphora also have this veinvein:
a tube-like, often darkened, structure on the wings
incomplete, but can be distinguished by their indistinct notaulinotaulus:
one of a pair of diverging furrows on the mesoscutum
). Kerita can be distinguished from the closely related genus Pseudodineura by the postocularpostocular:
describes area behind the compound eye
region of the head lacking fine pits (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.) and by the position of the ocelliocellus:
a simple bead-like eye, often on the dorsum of the head in groups of 1-3
.

Exotic pest species of concern

none

Host associations

Kerita fidala feeds on Mertensia virginica (Virginia bluebell) and possibly other Mertensia species (Smith 2009Smith 2009:
Smith DR. 2009. An obscure sawfly, Kerita fidala Ross (Hymenoptera: Tenthredinidae), new to Virginia, a leafminer of Virginia bluebell, Mertensia virginica (l.) Pers. Ex link (Boraginaceae). Banisteria 33: 53.). Hosts for the other species of Kerita are unknown (Smith 1976bSmith 1976b:
Smith DR. 1976b. World genera of the leaf-mining sawfly tribe Fenusini (Hymenoptera: Tenthredinidae). Insect Systematics and Evolution 7: 253-260.).

Life history

Larvae are leaf miners (Smith 1976bSmith 1976b:
Smith DR. 1976b. World genera of the leaf-mining sawfly tribe Fenusini (Hymenoptera: Tenthredinidae). Insect Systematics and Evolution 7: 253-260.). When disturbed, Pseudodineurini larvaelarva:
the immature stage of holometabolous insects
secrete the compound citral, which repels ants. This is presumably a beneficial defense strategy when they leave the mine to overwinter or pupate in the soil (Boevé et al. 2009).

Distribution

World: The genus is known only from North America (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.).

North America: Kerita fidala occurs in the Midwest, with records in Illinois and Indiana, and in Virginia (Smith 1976bSmith 1976b:
Smith DR. 1976b. World genera of the leaf-mining sawfly tribe Fenusini (Hymenoptera: Tenthredinidae). Insect Systematics and Evolution 7: 253-260., Smith 2009Smith 2009:
Smith DR. 2009. An obscure sawfly, Kerita fidala Ross (Hymenoptera: Tenthredinidae), new to Virginia, a leafminer of Virginia bluebell, Mertensia virginica (l.) Pers. Ex link (Boraginaceae). Banisteria 33: 53.). Kerita atira and K. difala occur in the west from California north to British Columbia and Alberta, east to Utah (Smith 1976bSmith 1976b:
Smith DR. 1976b. World genera of the leaf-mining sawfly tribe Fenusini (Hymenoptera: Tenthredinidae). Insect Systematics and Evolution 7: 253-260.).

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

Details about data used for maps can be found here.