Aprosthema

Taxonomy

Family: Argidae
Family common name: argid sawflies
Subfamily: Sterictiphorinae
Genus: Aprosthema Konow, 1899
Subgenera: none

Background

Argidae are found in all non-polar regions of the world (Smith and Middlekauff 1987Smith and Middlekauff 1987:
Smith DR and Middlekauff WW. 1987. Suborder Symphyta. In: Stehr FW ed. Immature Insects. Kendall/Hunt Publishing Company. Vol. 1: 754 pp., Smith 1992Smith 1992:
Smith DR. 1992. A synopsis of the sawflies (Hymenoptera: Symphyta) of America south of the United States: Argidae. Memoirs of the American Entomological Society 39: 1-201.). They are external foliage feeders with a wide range of host plants. Additionally, the family exhibits some uncommon behaviors like the excretion of defensive compounds and subsocialsubsocial:
Living in aggregations but lacking organizational structure as in true social insects; can describes insects with tendencies to protect or care for thier young, feed gregariously, and build cocoon masses.
habits (Smith 1992Smith 1992:
Smith DR. 1992. A synopsis of the sawflies (Hymenoptera: Symphyta) of America south of the United States: Argidae. Memoirs of the American Entomological Society 39: 1-201.).

Aprosthema are rarely collected, and most species worldwide are described from a few or from a single specimen. They are recognized by characteristic 3-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
, which in males are distinctly forked (Smith 1971cSmith 1971c:
Smith DR. 1971c. Nearctic sawflies of the genera Neoptilia Ashmead, Schizocerella Forsius, Aprosthema Konow, and Sphacophilus Provancher (Hymenoptera: Argidae). Transactions of the American Entomological Society 97: 537-594., Vikberg 2004Vikberg 2004:
Vikberg V. 2004. Seasonal head dimorphism and taxonomy of some European species of Aprosthema (Hymenoptera: Symphyta: Argidae). Beitrauml;ge Zur Entomologie 54 (1): 107-125. https://doi.org/10.21248/contrib.entomol.54.1.107-125).

Diversity

There are 57 described species restricted to the Northern Hemisphere. Species richness is relatively low in North America, with only two known species (Taeger et al. 2010Taeger et al. 2010:
Taeger A, Blank SM, and Liston AD. 2010. World Catalog of Symphyta (Hymenoptera). Zootaxa 2580: 1-1064.).

A key to North American species of Aprosthema is included in Smith 1971cSmith 1971c:
Smith DR. 1971c. Nearctic sawflies of the genera Neoptilia Ashmead, Schizocerella Forsius, Aprosthema Konow, and Sphacophilus Provancher (Hymenoptera: Argidae). Transactions of the American Entomological Society 97: 537-594..

Diagnostic characteristics

• three-segmented antennae; a single-segmented flagellumflagellum:
  the third section of the antennae that includes all the segments beyond the pedicel; segments of the flagellum are known as flagellomeres
  (Smith 1992Smith 1992:
  Smith DR. 1992. A synopsis of the sawflies (Hymenoptera: Symphyta) of America south of the United States: Argidae. Memoirs of the American Entomological Society 39: 1-201.)
• cenchri large and close together; distance between cenchricenchrus:
  a sclerotized eliptical lobe on the metascutum used to provide friction with underside of wings to hold them in place on the dorsum of the body while in rest
  less than width of cenchruscenchrus:
  a sclerotized eliptical lobe on the metascutum used to provide friction with underside of wings to hold them in place on the dorsum of the body while in rest
  (Smith 1992Smith 1992:
  Smith DR. 1992. A synopsis of the sawflies (Hymenoptera: Symphyta) of America south of the United States: Argidae. Memoirs of the American Entomological Society 39: 1-201.)
• metepimeron metepimeron:
  the dorsal portion of the metapleuron
  fused laterally with first tergitetergite:
  a sclerotized segment of the tergum
  (Smith 1992Smith 1992:
  Smith DR. 1992. A synopsis of the sawflies (Hymenoptera: Symphyta) of America south of the United States: Argidae. Memoirs of the American Entomological Society 39: 1-201.)
• tibiae with apicalapical:
  towards the apex; farthest away from the body
  spurs (Smith 1992Smith 1992:
  Smith DR. 1992. A synopsis of the sawflies (Hymenoptera: Symphyta) of America south of the United States: Argidae. Memoirs of the American Entomological Society 39: 1-201.)
• cell cell:
  1. a membranous area of the wing between veins, 2. a small cavity or closed space
  R open at apexapex:
  the end or most distal area of any structure
  (Smith 1992Smith 1992:
  Smith DR. 1992. A synopsis of the sawflies (Hymenoptera: Symphyta) of America south of the United States: Argidae. Memoirs of the American Entomological Society 39: 1-201.)
• slender, short palpipalpus:
  jointed structures emerging from the labium and maxilla
  (Smith 1992Smith 1992:
  Smith DR. 1992. A synopsis of the sawflies (Hymenoptera: Symphyta) of America south of the United States: Argidae. Memoirs of the American Entomological Society 39: 1-201.)
• head slightly anteriorly depressed between compound eyes (Smith 1992Smith 1992:
  Smith DR. 1992. A synopsis of the sawflies (Hymenoptera: Symphyta) of America south of the United States: Argidae. Memoirs of the American Entomological Society 39: 1-201.)
• male 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
  furcated; female 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
  clavate (Smith 1992Smith 1992:
  Smith DR. 1992. A synopsis of the sawflies (Hymenoptera: Symphyta) of America south of the United States: Argidae. Memoirs of the American Entomological Society 39: 1-201.)

May be confused with

The family Argidae can be distinguished by the single-segmented flagellumflagellum:
the third section of the antennae that includes all the segments beyond the pedicel; segments of the flagellum are known as flagellomeres
of the antennaantenna:
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 genus Aprosthema can be distinguished from other genera in the family by the lack of preapicalpreapical:
close to, but anterior to, the apex
spurs on the tibiaetibia:
the fourth segment of the leg, between the femur and the tarsus
, simple tarsal claws, and a lack of veinvein:
a tube-like, often darkened, structure on the wings
Sc in the fore wingfore wing:
the anterior wing of each pair of wings; usually the largest wing of the pair
. Males are distinguished from related genera Arge and Atomacera by the conspicuous forked 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
(Smith 1992Smith 1992:
Smith DR. 1992. A synopsis of the sawflies (Hymenoptera: Symphyta) of America south of the United States: Argidae. Memoirs of the American Entomological Society 39: 1-201.).

Exotic pest species of concern

none

Host associations

Larvae are external leaf feeders, and in North America feed on species of Fabaceae, including Acmispon grandifloras (chaparral bird’s-foot trefoil), Hosackia sp., and Lotus sp. (Smith 1992Smith 1992:
Smith DR. 1992. A synopsis of the sawflies (Hymenoptera: Symphyta) of America south of the United States: Argidae. Memoirs of the American Entomological Society 39: 1-201.). Other leguminous hosts such as Vicia cracca (bird vetch) and Lathyrus vernus (spring vetchling) are recorded for European species of Aprosthema (Vikberg 2004Vikberg 2004:
Vikberg V. 2004. Seasonal head dimorphism and taxonomy of some European species of Aprosthema (Hymenoptera: Symphyta: Argidae). Beitrauml;ge Zur Entomologie 54 (1): 107-125. https://doi.org/10.21248/contrib.entomol.54.1.107-125).

Life history

Little is known about the biology of Aprosthema. In other genera of Argidae, the female oviposits along the margin of the leaf. After hatching, the larvaelarva:
the immature stage of holometabolous insects
are external feeders on the foliage of plants (Smith 1989Smith 1989:
Smith DR. 1989. The sawfly genus Arge (Hymenoptera: Argidae) in the Western Hemisphere. Transactions of the American Entomological Society 115: 83-205.). Unlike other Argidae, larvaelarva:
the immature stage of holometabolous insects
of the genera of the subfamily Sterictiphorinae are not known to live or pupate in aggregations (Smith 1992Smith 1992:
Smith DR. 1992. A synopsis of the sawflies (Hymenoptera: Symphyta) of America south of the United States: Argidae. Memoirs of the American Entomological Society 39: 1-201.).

Distribution

World: This genus ranges throughout Europe, east into China and Russia, and in North America (Taeger et al. 2010Taeger et al. 2010:
Taeger A, Blank SM, and Liston AD. 2010. World Catalog of Symphyta (Hymenoptera). Zootaxa 2580: 1-1064.).

North America: Aprosthema is a western genus, with both North American species occurring in the Pacific Northwest (Washington, Oregon, California). Aprosthema brunniventre also occurs farther south into Nevada and Baja California Norte (Smith 1971cSmith 1971c:
Smith DR. 1971c. Nearctic sawflies of the genera Neoptilia Ashmead, Schizocerella Forsius, Aprosthema Konow, and Sphacophilus Provancher (Hymenoptera: Argidae). Transactions of the American Entomological Society 97: 537-594., Smith 1992Smith 1992:
Smith DR. 1992. A synopsis of the sawflies (Hymenoptera: Symphyta) of America south of the United States: Argidae. Memoirs of the American Entomological Society 39: 1-201., Taeger et al. 2010Taeger et al. 2010:
Taeger A, Blank SM, and Liston AD. 2010. World Catalog of Symphyta (Hymenoptera). Zootaxa 2580: 1-1064.).

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

Details about data used for maps can be found here.