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Phrontosoma

Taxonomy

Family: Tenthredinidae
Family Common Name: Common Sawflies
Subfamily: Allantinae
Tribe: Empriini
Genus: Phrontosoma MacGillivray, 1908
Subgenera: none

Background

The Tenthredinidae are the most species-rich family and are found throughout the world, in all continents but Antarctica. They are known as the “common sawflies.” They can generally be recognized by a cylindrical body and long, 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
. Otherwise, they come in a variety of colors, sizes, and forms (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.).

Sawflies in the Allantinae subfamily are mostly black and shining, sometimes with other colors. They have agricultural importance as some species are pests on cultivated and ornamental plants (Smith 1979aSmith 1979a:
Smith DR. 1979a. Nearctic sawflies. IV. Allantinae: Adults and larvae (Hymenoptera: Tenthredinidae). Technical Bulletin, U.S. Department of Agriculture 1595: 1-172.). They can be distinguished from other subfamilies by wing venationvenation:
the network of veins on a wing
(Smith 2003aSmith 2003a:
Smith DR. 2003a. A Synopsis of the sawflies (Hymenoptera: Symphyta) of America south of the United States: Tenthredinidae (Allantinae). Journal of Hymenoptera Research 12 (1): 148-192.).

Phrontosoma are medium-small in size, about 5–7 mm in length. All North American species are mostly black or black with orange thoracicthoracic:
of or on the thorax
sclerites (Smith 1979aSmith 1979a:
Smith DR. 1979a. Nearctic sawflies. IV. Allantinae: Adults and larvae (Hymenoptera: Tenthredinidae). Technical Bulletin, U.S. Department of Agriculture 1595: 1-172.).

Diversity

There are three described extantextant:
in existence; opposite of extinct
species worldwide, and all are NearcticNearctic:
describing the region of the Northern Hemisphere that includes North America south through northern Mexico
(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 NearcticNearctic:
describing the region of the Northern Hemisphere that includes North America south through northern Mexico
key to species is included in Smith 1979aSmith 1979a:
Smith DR. 1979a. Nearctic sawflies. IV. Allantinae: Adults and larvae (Hymenoptera: Tenthredinidae). Technical Bulletin, U.S. Department of Agriculture 1595: 1-172..

Diagnostic characteristics

Subfamily characters

  • fore wing fore wing:
    the anterior wing of each pair of wings; usually the largest wing of the pair
    vein M and 1m-cu parallel (Smith 1979aSmith 1979a:
    Smith DR. 1979a. Nearctic sawflies. IV. Allantinae: Adults and larvae (Hymenoptera: Tenthredinidae). Technical Bulletin, U.S. Department of Agriculture 1595: 1-172.    )
  • fore wing fore wing:
    the anterior wing of each pair of wings; usually the largest wing of the pair
    vein 2A+3A complete, connected to 1A by crossveincrossvein:
    short section of wing vein that connects two larger veins
     (Smith 1979aSmith 1979a:
    Smith DR. 1979a. Nearctic sawflies. IV. Allantinae: Adults and larvae (Hymenoptera: Tenthredinidae). Technical Bulletin, U.S. Department of Agriculture 1595: 1-172.    )
  • anal crossvein anal crossvein:
    a crossvein that goes through the center of the basal anal cell
    angled (Smith and Schiefer 1997Smith and Schiefer 1997:
    Smith DR and Schiefer TL. 1997. A new genus and species of Allantinae (Hymenoptera: Tenthredinidae) from southeastern United States. Proceedings of the Entomological Society of Washington 99 (3): 472-476.    )

Genus characters​

  • mandibles bidentatebidentate:
    having two teeth; often used in descrbing mandibles or tarsal claws
    (Smith 1979aSmith 1979a:
    Smith DR. 1979a. Nearctic sawflies. IV. Allantinae: Adults and larvae (Hymenoptera: Tenthredinidae). Technical Bulletin, U.S. Department of Agriculture 1595: 1-172.    )
  • clypeus clypeus:
    sclerotized area on the front of the head located between the antennal insertions and labrum
    very shallowly notched (Smith 1979aSmith 1979a:
    Smith DR. 1979a. Nearctic sawflies. IV. Allantinae: Adults and larvae (Hymenoptera: Tenthredinidae). Technical Bulletin, U.S. Department of Agriculture 1595: 1-172.    )
  • genal ridge present, but not extending past halfway up compound eye (Smith 1979aSmith 1979a:
    Smith DR. 1979a. Nearctic sawflies. IV. Allantinae: Adults and larvae (Hymenoptera: Tenthredinidae). Technical Bulletin, U.S. Department of Agriculture 1595: 1-172.    )
  • second antennal segment slightly longer than wide (Smith 1979aSmith 1979a:
    Smith DR. 1979a. Nearctic sawflies. IV. Allantinae: Adults and larvae (Hymenoptera: Tenthredinidae). Technical Bulletin, U.S. Department of Agriculture 1595: 1-172.    )
  • fore wing fore wing:
    the anterior wing of each pair of wings; usually the largest wing of the pair
    vein 2r present (Smith 1979aSmith 1979a:
    Smith DR. 1979a. Nearctic sawflies. IV. Allantinae: Adults and larvae (Hymenoptera: Tenthredinidae). Technical Bulletin, U.S. Department of Agriculture 1595: 1-172.    )
  • fore wing fore wing:
    the anterior wing of each pair of wings; usually the largest wing of the pair
    vein M intersecting Sc+R at the intersection of Sc+R and Rs+M (Smith 1979aSmith 1979a:
    Smith DR. 1979a. Nearctic sawflies. IV. Allantinae: Adults and larvae (Hymenoptera: Tenthredinidae). Technical Bulletin, U.S. Department of Agriculture 1595: 1-172.    )
  • tarsal claw tarsal claw:
    sharpened appendage emerging from the apex of the tarsus
    with indistinct basalbasal:
    towards the base; closest to the body
    lobe and long inner tooth (Smith 1979aSmith 1979a:
    Smith DR. 1979a. Nearctic sawflies. IV. Allantinae: Adults and larvae (Hymenoptera: Tenthredinidae). Technical Bulletin, U.S. Department of Agriculture 1595: 1-172.    )

May be confused with

Phrontosoma can be confused with similar species in the subfamily Allantinae or tribe Empriini. It can be distinguished by the combination of a short genal ridge, shallow clypealclypeus:
sclerotized area on the front of the head located between the antennal insertions and labrum
emargination, and bidentatebidentate:
having two teeth; often used in descrbing mandibles or tarsal claws
mandibles (Smith 1979aSmith 1979a:
Smith DR. 1979a. Nearctic sawflies. IV. Allantinae: Adults and larvae (Hymenoptera: Tenthredinidae). Technical Bulletin, U.S. Department of Agriculture 1595: 1-172.).

Exotic pest species of concern

none

Host associations

In North America, Phrontosoma usta feeds on Cornuscornus:
a pointed horn-like process on the apical end of the abdomen in Siricidae sawflies; on tergite 10 in females, sternite 9 in males
sp. (dogwood). No hosts are recorded for other species (Smith 1979aSmith 1979a:
Smith DR. 1979a. Nearctic sawflies. IV. Allantinae: Adults and larvae (Hymenoptera: Tenthredinidae). Technical Bulletin, U.S. Department of Agriculture 1595: 1-172.).

Life history

The biology of Phrontosoma is unknown. Other genera in the subfamily feed on leaves and pupate in the soil (Smith 1979aSmith 1979a:
Smith DR. 1979a. Nearctic sawflies. IV. Allantinae: Adults and larvae (Hymenoptera: Tenthredinidae). Technical Bulletin, U.S. Department of Agriculture 1595: 1-172.).

Distribution

World: This genus is known only from 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: All species of Phrontosoma occur commonly in the northeastern United States and eastern Canada. There are additional collections of P. belfragei in Texas and in Alberta. Phrontosoma brocca has also been collected in Corvallis, Oregon (Smith 1979aSmith 1979a:
Smith DR. 1979a. Nearctic sawflies. IV. Allantinae: Adults and larvae (Hymenoptera: Tenthredinidae). Technical Bulletin, U.S. Department of Agriculture 1595: 1-172.).

Map data from: GBIF.org (29 October 2019) GBIF Occurrence Download Phrontosoma

Details about data used for maps can be found here.