Arge

Taxonomy

Family: Argidae
Family common name: argid sawflies
Subfamily: Arginae
Genus: Arge Schrank, 1802
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. Additionally, the family exhibits some uncommon behaviors like the excretion of defensive compounds and subsocial habits (Smith 1992).

Arge are relatively large among the Argidae and can be up to 14 mm in length. Coloration can be highly variable, but in North America most adults are generally bright orange, black, or a combination of both (Smith 1989).

Diversity

Arge is an extremely speciose genus with 355 described species worldwide. Thirty-six species occur in North America (Taeger et al. 2010).

A key to Western Hemisphere species of Arge is included in Smith 1989.

Diagnostic characteristics

May be confused with

The family Argidae can be distinguished by the simple, single-segmented flagellum of the antenna. The genus Arge can be distinguished from other genera in the family by the presence of preapical spurs on the tibiae and the cells of the hind wing. Arge and Atomacera males lack the distinctive forked flagellum that other Argidae males possess (Goulet 1992).

Exotic pest species of concern

Arge ochropa, commonly known as the rose sawfly, is the “most serious pest of the flowers of Rosaceae” in Europe and western Asia (Khosravi et al. 2015). It as been intercepted at ports in New York and Chicago, and is established in Ontario (Smith 1989). In Iran, the species is a gregarious feeder on both the leaves and the flower buds. Adults also lay eggs into young stem tissue, potentially causing extensive damage to host plants (Khosravi et al. 2015).

There have been recent records of A. xanthogaster as a pest on wild and cultivated roses in India. This species is highly successful due to a combination of gregarious larval feeding, female parthenogenesis, and a multivoltine life cycle (Firake et al. 2013). It occurs in a temperate region of India, suggesting that, if introduced, the species could become a major pest of roses in North America (Forest Survey of India 2009).

Host associations

Larvae are external leaf feeders on a large variety of trees and shrubs from the genera Alnus (alder), Aronia (chokeberry), Betula (birch), Carpinus (hornbeam), Corylus (hazel), Crataegus (hawthorn), Diervilla (bush honeysuckle), Fragaria (strawberry), Hamamelis (witch-hazel), Ostrya (hop-hornbeam), Populus (cottonwood), Prunus (cherry), Pyrus (pear), Quercus (oak), Rhododendron (azalea), Rhus (sumac), Rosa (rose), Salix (willow), Sorbus (mountain-ash), Tilia (linden), and Ulmus (elm) (Smith 1989). There are also species that feed on Toxicodendron radicans (poison ivy), with A. humeralis even researched as a potential biological control agent for this noxious plant (Regas-Williams and Habeck 1979).

Life history

Females oviposit along the margin of the leaf. After hatching, the larvae are external feeders on the foliage of a plant, sometimes gregariously, sometimes singly (Smith 1989). Larvae are caterpillar-like, with variable coloration patterns and frequently body ornamentation in the form of tubercles or setae (Smith and Middlekauff 1987). At maturity, they can measure up to 25 mm in length (Furniss and Carolin 1977). Larvae overwinter as prepupae in cocoons in the soil or leaf litter underneath their host plant (Smith 1989).

There are a number of defenses that feeding larvae employ to deter predators. Like many sawflies, Arge use gregarious feeding behavior and aposematic coloring to warn against approach. Arge also harbor volatile compounds in their hemolymph that when secreted, can completely paralyze would-be insect predators. Because most of the host plants do not contain similar compounds, it is unclear how these chemicals are created in the body (Petre et al. 2007).

Arge is special among sawflies in its relatively late active season; adults fly in mid-summer, and larvae can be active into the fall. Most Nearctic species are univoltine, but those in more tropical or subtropical regions can have two or several generations per year (Smith 1989).

Some adults have been observed with pollen on the body while visiting flowers of plants other than the larval host, so Arge may play a role in pollination (Smith 1989).

Distribution

World: This genus is recorded in every continent, excluding Antarctica. It is especially diverse in Africa and Asia (Taeger et al. 2010). Only one species, A. basimacula, has a range extending into northern South America (Smith 1989) and one species, A. valida, is documented in the Australasian ecoregion (Taeger et al. 2010).

North America: Arge species are common throughout continental North America, from Alaska south through Canada and the United States (Smith 1989). The two southernmost species occur from Mexico to Panama, respectively (Smith 1989, Taeger et al. 2010). Arge ochropa is a European species established in Ontario, and has also been intercepted in Chicago and New York (Smith 1989).

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

Details about data used for maps can be found here.

Arge sp. female lateral habitus; photo by J. Orr, WSDA

Arge sp. female lateral habitus; photo by J. Orr, WSDA

Arge sparta female dorsal habitus; photo by J. Orr, WSDA

Arge sparta female dorsal habitus; photo by J. Orr, WSDA

Arge sparta female face; photo by J. Orr, WSDA

Arge sparta female face; photo by J. Orr, WSDA

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

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

Arge sp. male dorsal habitus; photo by J. Orr, WSDA

Arge sp. male dorsal habitus; photo by J. Orr, WSDA

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

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

Arge sparta wings; photo by J. Orr, WSDA

Arge sparta wings; photo by J. Orr, WSDA

Arge sparta antenna; photo by J. Orr, WSDA

Arge sparta antenna; photo by J. Orr, WSDA

Arge sparta female dorsal view of head and partial thorax; photo by J. Orr, WSDA

Arge sparta female dorsal view of head and partial thorax; photo by J. Orr, WSDA

Arge sp. lateral view of fused first tergite with the lateral pleura, a trait of Argidae and Pergidae; photo by J. Orr, WSDA

Arge sp. lateral view of fused first tergite with the lateral pleura, a trait of Argidae and Pergidae; photo by J. Orr, WSDA