Family common name: web-spinning and leaf-rolling sawflies
Genus: Cephalcia Panzer, 1803
Though the genus is fairly speciose, Cephalcia is not well-known in North America. They have distinctive larval habits that involve building elaborate nests of webs, leaf material, and frass, inside of which they feed and keep safe from predators. Some species can be recognized by the style of nest (Eidt 1969).
There are 43 described species worldwide, all restricted to the Northern Hemisphere. Ten species occur in North America (Taeger et al. 2010).
A key to North American species of Cephalcia is included in Middlekauff 1958.
Pamphiliidae are recognized by a somewhat quadrate head and tarsal claws, often with inner teeth. Cephalcia can be distinguished from Acantholyda by the lack of a preapical spur on the inner side of fore leg and from other genera in the family by the small inner tarsal claw tooth (Goulet 1992).
Three Palearctic Cephalcia species have caused extensive damage to Picea abies (Norway spruce) stands in their native ranges. Cephalcia abietis, also known as the false spruce webworm, has had recorded outbreaks of up to 136,000 acres in Germany and the region formerly known as Czechoslovakia in recent decades (Führer and Fischer 1991). Cephalcia arvensis was responsible for severe defoliation of more than 3700 acres over a six-year period in central Europe (Marchisio et al. 1994). Cephalcia masuttii is also documented on Picea abies. Despite being more patchily distributed than the other two species, it has gregarious feeding habits that result in extensive damage where it is present (Battisti and Boato 1998). Picea abies is introduced to North America, and has a fairly wide distribution in northern regions, so these pest species would find ample host material if introduced (Sullivan 1994).
Cephalcia lariciphilia in Europe and Asia feeds heavily and gregariously on Larix decidua (European larch) and has historically reached outbreak levels. There are currently no records of Cephalcia on larch in North America. Larix decidua is grown in the northern United States and southern Canada as a timber species, and this sawfly, if introduced, could potentially damage this and other native larch species (Georgis and Hague 1988, Sullivan 1994, Holusa and Kuras 2010).
Cephalcia pinivora is a pest of Pinus massoniana in China, which is not widely grown in North American forests. It is unknown if there are alternative hosts (Xiao and Zeng 1998)
Larvae feed on needles of numerous species of Pinaceae including: Pinus contorta (lodgepole pine), Pinus ponderosa (ponderosa pine), Pinus resinosa (red pine), Pinus banksiana (jack pine), Pinus strobus (white pine), Picea glauca (white spruce), Picea rubens (red spruce), Picea engelmanni (Engelmann spruce), Picea pungens (blue spruce), Picea mariana (black spruce), Picea sitchensis (Sitka spruce), Abies balsamea (balsam fir), and Tsuga canadensis (eastern hemlock) (Eidt 1969).
The female makes a small slit in the side of a mature needle and deposits the egg so that the membrane gets caught in the slit, ensuring the egg stays in place on the outside of the needle, yet allowing the egg to be in contact with vascular tissue and obtain moisture. After hatching, larvae commence building a structure for protection. Cephalcia larvae are able to spin silk, and this silk is used to transport substrate and to build a shelter of needles in which they safely feed and molt. They eat by using mandibles to cut small needles at the base, bringing the needle into their shelter, and feeding from base to apex (Eidt 1969).
Mature larvae drop to the ground and burrow into the soil to a depth of 5–15 cm. These prepupae then build a small overwintering cell of soil and silk. In spring, they pupate and emerge. Adults fly in early summer, May to June, and generally only live for about 5 days. Many Cephalcia are univoltine, but some have two or more year-long life cycles (Eidt 1969).
World: The genus is common in northern and central Europe, eastwards through northern Asia to China (Van Achterberg and Van Aartsen 1986).
Map data from: GBIF.org (26 June 2019) GBIF Occurrence Download Cephalcia
Details about data used for maps can be found here.