Sphacophilus

Taxonomy

Family: Argidae
Family common name: argid sawflies
Subfamily: Sterictiphorinae
Genus: Sphacophilus Provancher, 1888
Subgenera: Sphacophilus, Ceocolus, Litocolus

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).

Sphacophilus are about 6–10 mm in length, and are generally orange and black in color. They are fairly speciose and have an extensive range throughout the Americas. Although they have been classified into three separate subgenera, these groupings may be revised over time, as more species are discovered that do not fit the defined subfamilies (Smith 1971c, Smith 1992).

Diversity

There are 52 species described worldwide, all but one restricted to the Americas. The majority of species occur in North America, and the highest diversity is recorded in Central America and Mexico (Smith 1992, Taeger et al. 2010, Monjarás-Barrera et al. 2015, Smith 2017b).

A key to North American species of Sphacophilus is included in Smith 1971c.

Diagnostic characteristics

May be confused with

The family Argidae can be distinguished from other sawflies by the single-segmented flagellum of the antenna. The genus Sphacophilus can be distinguished from other genera in the family by the wing venation, palpi length, lack of vein Sc, and a lack of preapical tibial spurs. Males are distinguished from related genera Arge and Atomacera by the conspicuous forked antennae (Smith 1992).

Exotic pest species of concern

Sphacophilus monjarasi is an agricultural pest in southern Mexico and Central America, where it feeds on a regionally important food crop, Crotalaris longirostrata, commonly known as chipilín. Chipilín is also grown in some regions of the United States (Monjarás-Barrera et al. 2015).

Host associations

Many species have been observed as external leaf feeders on a large variety of trees and shrubs from the Fabaceae and Convolvulaceae. Confirmed genera include Ipomoea (morning glory), Convolvulus (bindweed), Psoralea, Desmodium (tick clover), and Delea (prairie clover). One species in Costa Rica is known from Fabaceae Hymenaea courbaril (West Indian Locust), another from Malpighiaceae Heteropterys laurifolia (dragon withe), and one species in the southwestern United States has been reared from Polygonaceae species Eriogonum wrightii (bastardsage) (Smith and Middlekauff 1987, Smith 1992, Smith and Janzen 2003). Sphacophilus apios feeds on Apios americana (potato bean) (Ross 1933, Taeger et al. 2010). Important agricultural host records include Sphacophilus cellularis feeding on Ipomoea batatas (sweet potato), and Sphacophilus monjarasi on Crotalaria longirostrata (chipilín) (Smith 1971c, Monjarás-Barrera et al. 2015). The host for many species is unknown (Monjarás-Barrera et al. 2015).

Life history

Larvae are only known for 3 Nearctic species (S. cellularis, S. nigriceps, S. apios). All three species have black or brown head capsules with black spots around the ocelli and on the apex of the mandible, and green bodies with short dark-colored tubercles throughout and a set of long spines at the apex of the abdomen (Ross 1933, Smith 1972, BugGuide 2019).

Scattered records from Central America provide some information on larval habits. Small green larvae of S. janzeni feed on new leaf growth of young plants in a semi-circular pattern, and build brown oval cocoons that they attach to leaf fragments or stems in the leaf litter. Sphacophilus manjarasi has similar habits, but builds its cocoon on the still-standing, defoliated stem of the plant. Species reared from tropical regions in Central America do not undergo dormancy or diapause, and eclose after just 1–2 weeks as a pupa (Smith and Janzen 2003, Monjarás-Barrera et al. 2015).

Distribution

World: This genus ranges from as far north as Canada, as far south as Bolivia (Smith 1992, Smith 2017b). One species, Sphacophilus afer, is recorded from tropical Africa (Cameroon) (Liston et al. 2017).

North America: Sphacophilus ranges from southern Canada, south through the United States, Mexico, and Central America. There are no records in the Caribbean Islands (Smith 1992).

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

Details about data used for maps can be found here.

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

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

Sphacophilus sp. female dorsal habitus; photo by J. Orr, WSDA

Sphacophilus sp. female dorsal habitus; photo by J. Orr, WSDA

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

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

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

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