Family common name: common sawflies
Genus: Monsoma MacGillivray, 1908
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).
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 1979a). They can be distinguished from other subfamilies by wing venation (Smith 2003a).
Monsoma are medium-sized, about 6–8 mm in length. The two North American species are distinct, one mostly orange/yellow, the other mainly black (Smith 1979a, Smith and Goulet 2000, Kruse et al. 2010).
Monsoma can be confused with similar species in the subfamily Allantinae or tribe Empriini. It can be distinguished from most other genera by the complete genal ridge and the tarsal claw basal lobe. It is especially similar to Empria, which can be recognized by paired white spots on the abdomen (Smith 1979a).
Monsoma pulveratum is native to the Eastern Hemisphere, but was discovered in North America in Newfoundland in 1991 (Smith and Goulet 2000). It became established in Alaska by 2007, where it caused significant defoliation of alder stands in the south-central area of the state (Kruse et al. 2010). In 2012, the species was detected in several sites in Idaho, Washington, and Oregon, but has not caused the severe defoliation observed in Alaska (Looney et al. 2012).
In North America, Monsoma feeds on Alnus (alder). One collection of M. inferentium in British Columbia was made on Salix (willow) (Smith 1979a).
Monsoma pulveratum is native to the Eastern Hemisphere, but was discovered in North America in Newfoundland in 1991 (Smith and Goulet 2000). The larvae of M. pulveratum are bright green with green and white stripes and white spots surrounding the spiracles (Kruse et al. 2010). Feeding behavior is characterized by complete defoliation when populations are high; at lower densities feeding damage appears as a series of small holes in leaves (Looney et al. 2012). Males have not been collected in North America, suggesting that this species may reproduce parthenogenetically (Smith and Goulet 2000).
North America: Monsoma pulveratum is recorded in Newfoundland, Alaska, Washington, Idaho, Oregon, and Montana (Kruse et al. 2010, Looney et al. 2012). Monsoma inferentium is recorded throughout the northeastern United States and eastern Canada, with some collections farther west in Alberta and British Columbia (Smith 1979a).
Map data from: GBIF.org (29 October 2019) GBIF Occurrence Download Monsoma
Details about data used for maps can be found here.