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 Heterarthrinae subfamily are generally small and dark-colored. Many species of this family are economic pests of trees and shrubs and can be characterized by their skeletonizing or leaf-mining larval feeding behaviors. Heterarthrinae adults can be distinguished from those of other subfamilies by wing venation (Smith 1971a).
Caliroa is a species-rich genus found throughout the world. Most species are small, about 4.5–5 mm in length, and mostly black, often with pale-colored legs (Smith 1971a). Unlike other genera in the subfamily, Caliroa and Endelomyia are external leaf feeders and not leaf miners (Goulet 1992).
An incomplete key to species is included in Smith 1971a.
Caliroa can easily be distinguished from other genera in the subfamily by the complete anal cell with crossvein, number of antennal segments, and narrow malar space (Goulet 1992). It can be confused with the similar genus Endelomyia, but is distinguished by the apical flagellomeres (Smith 1967c).
Caliroa cerasi is a common pest of agricultural significance. Though its common name is “pear slug,” the species has several hosts and is responsible for severe defoliation of agricultural and ornamental plants (Raffa and Lintereur 1988). The “slug” part of the common name comes from the larval form being long, slimy, and shining (Miles 1935). The species is usually bivoltine in North America (Smith 1971a). This species has spread via exportation of wood and fruit products and is invasive and established in Australia, South America, and South Africa (Koch and Smith 2011).
Caliroa quercuscoccineae is a pest of red oak responsible for infestations defoliating more than 1.5 million acres of trees in a single year. Recent years have seen a decrease of outbreaks of this species (Nordin and Johnson 1983).
Caliroa in North America feeds on a variety of plants including species of Quercus (oak), Nyssa (tupelo), Castanea (chestnut), Pyrus (pear), Prunus (cherry, plum), Sorbus (mountain ash), Malus (apple), Salix (willow), Cotoneaster, and Chaenomeles (flowering quince) (Raffa and Lintereur 1988, Goulet 1992, Smith 2003b). Caliroa dionae feeds on Vaccinium corymbosum (highbush blueberry) (Smith and Moisan-De Serres 2017).
Females oviposit into the surface of the leaf, along the midrib or a main vein. Larvae feed gregariously for a few weeks on the inter-vein tissue, skeletonizing the leaf. At maturity, the larvae drop to the ground and pupate or overwinter. Many species are multivoltine (Smith 1971a).
World: This genus is represented in every continent except Antarctica. Species range throughout North America, South America, Europe, Japan, and China, and occur in Indonesia, Australia, and South Africa (Smith 2003, Koch and Smith 2011).
North America: Caliroa occurs throughout the United States and southern Canada, with some records in Mexico (Smith 1971a, Smith 2003).
Map data from: GBIF.org (29 October 2019) GBIF Occurrence Download Caliroa
Details about data used for maps can be found here.