Pristiphora

Taxonomy

Family: Tenthredinidae
Family common name: common sawflies
Subfamily: Nematinae
Tribe: Nematini
Genus: Pristiphora Latreille, 1810
Subgenera: unresolved

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 antennae. Otherwise, they come in a variety of colors, sizes, and forms (Goulet 1992).

Nematinae is the second-largest subfamily of Tenthredinidae, with over 1,250 species (Prous et al. 2014). They are most diverse in northern Eurasia and North America; only a few species occur in the Southern Hemisphere. Nematinae sawflies have a variety of feeding habits including external leaf feeding, leaf mining, and gall forming, and feed on a variety of hosts (Smith 2003b).

The Nematinae have been subject to numerous revisions in recent years. As of 2021, there are no comprehensive keys to many of the North American species of Nematinae (Prous et al. 2014). Because of changing taxonomy and extreme variability in morphology, identifying genera and species in the Nematinae may be more challenging than in other subfamilies of Tenthredindae. For this reason, knowing the host or behaviors of a specimen can be extremely helpful for identification within this subfamily.

Pristiphora is an extremely species-rich genus with a widespread distribution. In recent years, several genera including Neopareophora, Nepionema, Melastola, and Pristola were collapsed into Pristiphora based on molecular phylogenetics. This makes the genus especially difficult to key based on morphology (Prous et al. 2014, Prous et al. 2017).

Pristiphora are about 4–8 mm in length and have a variety of colors and forms (Smith 2003b). The genus includes several pest species of economic importance (Smith and Middlekauff 1987).

Diversity

There are 221 described species worldwide. About 55 species occur in North America north of Mexico (Taeger et al. 2018).

Diagnostic characteristics

Subfamily characters

Genus characters

There are several forms represented in Pristiphora, so some characters only apply to some species:

May be confused with

Pristiphora has several shared morphological characters with Euura and Nematus, and in some cases cannot be easily distinguished. Together, these three genera can usually be distinguished from other Nematinae by the lack of fore wing vein 2r-rs, incomplete vein 2A+3A, and asymmetrical outer surfaces of the mandibles. Pristiphora can usually be distinguished from Euura and Nematus by the apically emarginate ovipositor sheath, short inner tooth of the tarsal claw (or tarsal claw simple), apically truncate clypeus (or clypeus very shallowly emarginate), and apically enlarged fore wing vein C (Prous et al. 2014). Some species of Pristiphora have fore wing vein 2r-rs present, while others lack a basal anal cell on the hind wing; the latter species can be distinguished from other similar genera by the diagnostic characters listed above.

Exotic pest species of concern

Pristiphora abietina, the little spruce sawfly, has been recorded causing defoliation in huge infestations on spruce in Central Europe. Because the larvae feed only on new growth, the trees are not fully defoliated and therefore do not die, so the insect is arguably not a significant pest even when present in high abundance (Holusa and Drápela 2003).

Native or introduced pest species

Pristiphora erichsonii is a native pest of western larch and tamarack that has been recorded causing extensive damage, and sometimes death, in these important forestry trees. The female oviposits into new shoots, usually depositing dozens of eggs in a single site. The larvae feed gregariously on the needles until maturity when they drop to the soil and form cocoons in moist peat. Pristiphora erichsonii is univoltine (Turnock 1960).

There are several Pristiphora pests introduced from Europe. Pristiphora abbreviata, commonly known as the California pear sawfly, occasionally causes significant damage to pear trees (Smith 1967d)Pristiphora geniculata is a pest of mountain ash known as the mountain ash sawfly. It has caused severe defoliation of its host, which is used as a forestry regeneration plant. The introduced parasite Olesicampe geniculatae has been an effective biocontrol agent of this pest in Canada (Quednau 1990)Pristiphora appendiculata, the black currant sawfly, is a pest of cultivated currants (Zinovjev and Smith 2000b), and Pristiphora rufipes, the columbine sawfly, is a pest of columbine plants (Smith 2013).

Host associations

In North America, Pristiphora feeds on a variety of hosts, including species of Betula (birch), Vaccinium (blueberry), Salix (willow), Quercus (oak), Ribes (currant, gooseberry), Rubus (raspberry), Prunus (cherry, plum, pear), Rosa (rose), Sorbus (mountain ash), Aquilegia (columbine), and Larix (larch) (Quednau 1990, Goulet 1992, Smith 2003b).

Life history

Life histories are varied in the genus Pristiphora, but they are generally solitary external leaf feeders (Smith and Middlekauff 1987). Larvae of some species (e.g. P. erichsonii) are gregarious, and can cause notable defoliation.

Distribution

World: The genus is known from North America, throughout Europe, and in western Asia and East Asia (Togashi and Tano 1987, GBIF), Malaysian Borneo (Haris 2006), Colombia, Venezuela, and Brazil (Smith 2003b).

North America: Pristiphora occurs throughout the United States and Canada north into Alaska, Yukon, the Northwest Territories, and Nunavut (Prous et al. 2017, GBIF). Several species are known from Mexico and Costa Rica (Smith 2003b). There are several species introduced from Europe in the early twentieth century that have since become established (see Life history topic for details on these species).

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

Details about data used for maps can be found here.

Pristiphora acidovalva female lateral habitus; photo by J. Orr, WSDA

Pristiphora acidovalva female lateral habitus; photo by J. Orr, WSDA

Pristiphora abbreviata female face; photo by J. Orr, WSDA

Pristiphora abbreviata female face; photo by J. Orr, WSDA

Pristiphora banksi male lateral habitus; photo by J. Orr, WSDA

Pristiphora banksi male lateral habitus; photo by J. Orr, WSDA

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

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

Pristiphora banksi male face; photo by Q. Baine, WSDA

Pristiphora banksi male face; photo by Q. Baine, WSDA

Pristiphora acidovalva wings; photo by P. Jones, WSDA

Pristiphora acidovalva wings; photo by P. Jones, WSDA