The Diprionidae are known as the conifer sawflies, though they are not the only family to use conifer trees as host (others include Siricidae, Pamphiliidae, Xyelidae, some genera of Tenthredinidae). Many are destructive pests as larvae, and so their biology has been more extensively studied than some other groups. Diprionids have stout bodies and distinctive antennal characteristics that make adults easy to recognize (Furniss and Carolin 1977).
Neodiprion is widespread and fairly common in conifer tree-growing regions. Adults are about 7.5–10 mm in length and are generally red or reddish-brown in color. Several species can be destructive defoliators (Ciesla and Smith 2011).
There are 53 described species worldwide. Richness is highest in North America, where all but six species occur (Taeger et al. 2010).
Diprionidae are most easily recognized by the distinctive antennae of both sexes, but also are characterized by small, stout bodies. Neodiprion is similar to Gilpinia, but the latter has notably large cenchri, a small mesoscutellum, and a distinct anterior margin of the mesoscutellum (Smith 1971b, Goulet 1992).
Defoliating Neodiprion species described from China are recorded feeding on species of pines that are not commonly grown in North America, but are occasionally used as ornamental plants: Pinus armandii and P. yunnanensis (Li et al. 2012).
Larvae in North America feed on several species of Pinus (pine), Picea (spruce), Tsuga (hemlock), Pseudotsuga (Douglas fir), and Abies (fir) of the Pinaceae (Smith 1974b). Common hosts include Pinus ponderosa (ponderosa pine), Pinus resinosa (red pine), and Pinus contorta (lodgepole pine) (Ciesla and Smith 2011).
Neodiprion females oviposit into slits cut longitudinally along the needle. After hatching, larvae feed gregariously from the tip of the needle to the base. As they mature, larvae will separate from one another and feed singly in later instars. Larvae prefer to feed on older needles and transfer to new growth only after majority of the old growth has been eaten. At maturity, the larva falls to the ground and builds a cocoon in the leaf litter. Depending on the generation, they will pupate or overwinter as a prepupa and eclose in the spring. Some Neodiprion species overwinter in the egg stage and hatch in the spring (Ciesla and Smith 2011).
Larvae of Neodiprion have some uncommon defensive strategies. When disturbed, the larvae rear their heads and front portion of the body, moving up and down in unison to surprise or confuse predators. Larvae also sometimes will deposit regurgitated pine resin onto the body of a predator or parasite (Ciesla and Smith 2011).
Many Neodiprion species are economic pests, and outbreaks of some species in pine stands have historically caused significant damage. Coniferous trees do not regrow foliage every year, so heavy defoliation, especially in combination with other stress, can lead to mortality (Furniss and Carolin 1977, Ciesla and Smith 2011). Neodiprion sertifer, the European pine sawfly, was introduced in the early twentieth century and is established in North America as a pest (Furniss and Carolin 1977).
World: Several species of Neodiprion occur in China and other parts of East Asia. Neodiprion sertifer has a range extending from Europe, through Siberia, and into Japan, and is also present in North America (Smith 1974b).
North America: Neodiprion is widespread in North America, with species recorded throughout southern Canada and the United States south into Central America and Cuba. Neodiprion sertifer was introduced to North America and was first discovered in the eastern United States in 1925 and then in Canada in 1939. It is now established in several states and provinces (Lyons 1964, Smith 1974b, Looney et al. 2016).
Map data from: GBIF.org (26 June 2019) GBIF Occurrence Download Neodiprion
Details about data used for maps can be found here.