Family common name: stem sawflies
Genus: Calameuta Konow, 1896
Subgenera: Calameuta, Ephemerocephus
The Cephidae are commonly known as “stem sawflies” because larvae feed and live within the stems of small herbaceous and woody plants. Many are considered pests as this feeding behavior can damage or kill the plant host (Shanower and Hoelmer 2004).
Stem sawflies of the genus Calameuta are generally slender, with slightly laterally compressed cylindrical bodies. They have a black head and black body with yellow markings. There is a slight constriction at the second abdominal segment, giving it the gestalt of a wasp (Middlekauff 1969). The body length varies from 4–10 mm on average (Benson 1951).
Worldwide, there are 23 described species restricted to the Northern Hemisphere. Only two species are known to occur in North America (Taeger et al. 2010).
A key to North American species of Calameuta is included in Smith and Schiff 2005.
Calameuta can be confused with other Cephidae, especially Trachelus and Cephus which were previously in this genus. They can be distinguished from Trachelus by the lack of bristled pits on sternite 7 and 8 of the male, and from Cephus by the bidentate left mandible and lack of long scale-like setae on sternite 8 of the male. They can be separated from other genera of Cephidae by the presence of preapical spurs on the hind tibiae, flagellomere 3 subequal to 4, and the distinctly clavate antennae beginning past the midpoint (Ries 1937, Middlekauff 1969, Smith and Schiff 2005).
Few host plants for Calameuta have been confirmed in North America. One hypothesis based on shared range is that this species feeds on wild grasses Bromus laevipes (Chinook brome) and/or Deschampsia danthoniodes (annual hairgrass) (Smith and Schiff 2005). In Europe, known host plants include grasses such as Alopecurus pratensis (meadow foxtail) Calamagrostis epigejos (bushgrass), Phragmites communis (common reed), Elymus repens (couch grass), Arrhenatherum elatius (false oat grass), and Phalaris arundinacea (reed canary grass) (Benson 1951).
Female Calameuta oviposit into larger-diameter stems of grasses (Middlekauff 1969, Shanower and Hoelmer 2004). After hatching, larvae feed on the vascular tissue of the plant, moving downwards towards the base (Shanower and Hoelmer 2004). Larvae are creamy white and grub-like in appearance. They lack abdominal prolegs and have vestigial thoracic legs. All Cephidae larvae possess a tubular dorsal horn on the posterior end of the body (Middlekauff 1969). As they feed, they use this horn to pack frass in the gallery behind them. At the base of the plant, the larvae girdle the stem above themselves by chewing a V-shaped notch along the inner wall, then pack frass tightly between themselves and this point. When the plant weakens and dies from the damage, it breaks off at this point and leaves a stub in the ground with a frass plug on top, keeping the larva safe inside (Shanower and Hoelmer 2004).
Larvae generally undergo a period of diapause, either over winter or through a dry season, then pupate inside the stub. After about 2 weeks, the adult chews or pushes its way out of the stub and emerges. In cultivated crops, adults generally live for only 7–10 days and are univoltine (Shanower and Hoelmer 2004).
World: The genus is widespread in the Palearctic region with records throughout Europe east into Russia, south to the Mediterranean (Taeger et al. 2006), and in North Africa, Central Asia, China, and Japan (Benes and Holusa 2015, Discover Life 2019).
North America: The two species of North America are sympatric, both occurring in the Pacific Northwest United States with records in California, Oregon, Washington, and Idaho (Smith and Schiff 2005).
Map data from: GBIF.org (26 June 2019) GBIF Occurrence Download Calameuta
Details about data used for maps can be found here.