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 1987, Smith 1992). 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 subsocial habits (Smith 1992).

Atomacera are small among the Argidae and usually measure less than 5 mm in length (Smith 1992). In North America, the adults are mostly black with simple antennae and infuscated wings (Lindquist and Trinnell 1965).

Diversity

There are 34 described species worldwide, restricted to the New World. Thirteen species occur in North America with the highest diversity in the Central American region (Smith 1992, Taeger et al. 2010).

A key to Nearctic species of Atomacera is included in Smith 1969c.

Diagnostic characteristics

May be confused with

The family Argidae can be identified by the simple, single-segmented flagellum of the antenna. The genus Atomacera can be distinguished by the tarsal claw and toothed mandible. Arge and Atomacera males lack the distinctive forked flagellum that other Argidae males possess (Goulet 1992).

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 1992).

Life history

Females oviposit into small “pockets” they cut into the upperside of the leaf. Larvae feed gregariously in groups of 10–12 on the parenchyma of the leaf from the underside, leaving the leaf looking translucent and skeletonized with only the cuticle and venation intact. At maturity, they fall to the ground and spin cocoons in leaf litter underneath the plant (Lindquist and Trinnell 1965, Tippins 1965). North American Atomacera are multivoltine, with 2–6 generations per year (Tippins 1965).

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 1992).

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 1992).

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

Details about data used for maps can be found here.

Atomacera debilis female lateral habitus; photo by J. Orr, WSDA

Atomacera debilis female lateral habitus; photo by J. Orr, WSDA

Atomacera debilis female dorsal habitus; photo by J. Orr, WSDA

Atomacera debilis female dorsal habitus; photo by J. Orr, WSDA

Atomacera sp. female face; photo by J. Orr, WSDA 

Atomacera sp. female face; photo by J. Orr, WSDA 

Atomacera sp. male lateral habitus; photo by J. Orr, WSDA

Atomacera sp. male lateral habitus; photo by J. Orr, WSDA

Atomacera sp. male face; photo by J. Orr, WSDA

Atomacera sp. male face; photo by J. Orr, WSDA

Atomacera sp. fore wing; photo by J. Orr, WSDA

Atomacera sp. fore wing; photo by J. Orr, WSDA