Atomacera

Taxonomy

Family: Argidae
Family common name: argid sawflies
Subfamily: Atomacerinae
Genus: Atomacera Say, 1836
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. 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.).

Atomacera are small among the Argidae and usually measure less than 5 mm in length (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.). In North America, the adults are mostly black with simple 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
and infuscated wings (Lindquist and Trinnell 1965Lindquist and Trinnell 1965:
Lindquist OH and Trinnell JR. 1965. The trefoil sawfly, Atomacera debilis Say (Hymenoptera: Argidae), in Ontario. The Canadian Entomologist 97: 181-184.).

Diversity

There are 34 described species worldwide, restricted to the New WorldNew World:
the Western Hemisphere; the continents of North and South America
. Thirteen species occur in North America with the highest diversity in the Central American region (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.).

A key to NearcticNearctic:
describing the region of the Northern Hemisphere that includes North America south through northern Mexico
species of Atomacera is included in Smith 1969cSmith 1969c:
Smith DR. 1969c. Key to genera of Nearctic Argidae (Hymenoptera) with revisions of genera Atomacera Say and Sterictiphora Billberg. Transactions of the American Entomological Society 95: 439-457..

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.)
• mid and hind tibiaetibia:
  the fourth segment of the leg, between the femur and the tarsus
  without preapicalpreapical:
  close to, but anterior to, the apex
  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
  R1 of hind winghind wing:
  the posterior wing of each pair of wings
  open at apexapex:
  the end or most distal area of any structure
  (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.)
• tarsal claw tarsal claw:
  sharpened appendage emerging from the apex of the tarsus
  with large lobe at basebase:
  the beginning or most proximal area of any structure
  (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.)
• mandible mandible:
  the primary mouthpart used for biting and chewing; jaw
  with 3 large teeth (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.)
• fore wing fore wing:
  the anterior wing of each pair of wings; usually the largest wing of the pair
  with intercostal crossveincrossvein:
  short section of wing vein that connects two larger veins
  ; Sc veinvein:
  a tube-like, often darkened, structure on the wings
  present in fore wingfore wing:
  the anterior wing of each pair of wings; usually the largest wing of the pair
  (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 identified by the simple, 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 Atomacera can be distinguished by the tarsal clawtarsal claw:
sharpened appendage emerging from the apex of the tarsus
and toothed mandiblemandible:
the primary mouthpart used for biting and chewing; jaw
. Arge and Atomacera males lack the distinctive forked flagellumflagellum:
the third section of the antennae that includes all the segments beyond the pedicel; segments of the flagellum are known as flagellomeres
that other Argidae males possess (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

Larvae of Argidae are external leaf feeders on a large variety of plants. The only confirmed host records for Atomacera are for the two northernmost species: A. debilis feeds on species of Desmodium, with collections from Desmodium canadense (showy tick-trefoil) and Desmodium glutinosum (pointed leaf tick-trefoil). Atomacera decepta feeds on many species of ornamental Hibiscus (rosemallow). One specimen of A. pubicornis from Trinidad was associated with Ipomoea sp. (sweet potato, bindweed) (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.).

Life history

Females oviposit into small “pockets” they cut into the upperside of the leaf. LarvaeLarva:
the immature stage of holometabolous insects
feed gregariously in groups of 10–12 on the parenchymaparenchyma:
in plants, the soft, thin-walled, inner tissue that performs functions such as photosynthesis, storage, and secretion; as opposed to dermal and vascular tissues
of the leaf from the underside, leaving the leaf looking translucent and skeletonized with only the cuticle and venationvenation:
the network of veins on a wing
intact. At maturity, they fall to the ground and spin cocoons in leaf litter underneath the plant (Lindquist and Trinnell 1965Lindquist and Trinnell 1965:
Lindquist OH and Trinnell JR. 1965. The trefoil sawfly, Atomacera debilis Say (Hymenoptera: Argidae), in Ontario. The Canadian Entomologist 97: 181-184., Tippins 1965Tippins 1965:
Tippins HH. 1965. The sawfly Atomacera decepta , a pest of Hibiscus . Journal of Economic Entomology 58 (1): 161-162. https://doi.org/10.1093/jee/58.1.161a). North American Atomacera are multivoltinemultivoltine:
describing a life cycle with many generations per calendar year
, with 2–6 generations per year (Tippins 1965Tippins 1965:
Tippins HH. 1965. The sawfly Atomacera decepta , a pest of Hibiscus . Journal of Economic Entomology 58 (1): 161-162. https://doi.org/10.1093/jee/58.1.161a).

Distribution

World: This genus is restricted to the Americas, from eastern Canada and the United States, through the Caribbean and Central America, south to northern Argentina (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.).

North America: Most Atomacera range from Panama north to the southern United States, with 2 species occurring farther north east of the Mississippi River and north into eastern Canada. One species, A. pubicornis, is recorded in Trinidad and Tobago in the Caribbean (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.).

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

Details about data used for maps can be found here.