Cerodontha (Poemyza) incisa (Meigen, 1830)
Spencer, 1973 mentioned C. pygmeae as closely related to incisa. He mentioned as only difference the light squamal fringe in the latter species. Neither the male genitalia nor the host range is reliable for distinction of the two species. The following illustration is from Nowakowski, 1973: (Cer pygmeae.pct).
FURTHER IMPORTANT CHARACTERS
Adults
Wing length: 2.3 - 2.75 mm. Sclerotization of ocellar triangle clearly not extended beyond ocelli. Squamae with light setulae. Mesonotum with some (four) enlarged posterior acrostichal bristles, irregularly distributed. Mesonotum and tergites shining with fine pubescence. Hyaline light margins of anepisternum rather broad. Frons and cheeks are lightish, but appearing dark because of rather strong dark denticles covering the surface.
Immature stages
Cephalopharyngeal skeleton (Cer incisa ceph.pct): Mandibles long and wide with altogether four regularly alternating mouth hooks of equal size. Intermediate sclerite and basal sclerite of cephalopharyngeal skeleton slender, basal sclerite weakly sclerotized, ventral arm distinctly longer than half as long as dorsal arm.
Anterior spiracles wide with well separated terminal bulbs situated in a single row. Posterior spiracles of larva arising from conical projection. The three bulbs on each spiracle are nearly of equal size. On each side of the spiracles there is a conspicuous dark patch (Nowakowski, 1973: "Raspelwarzen") (fig. SEM or from Nowakowski). Puparium deeply segmented, shining black, with bluish or purplish reflections.
BIONOMICS
The larva forms a long whitish mine in the leaf blade, sometimes several feeding together. There are at least two generations per year (Spencer, 1973).
As in the other subgroups of Cerodontha, the puparia remains inside the mine but the way of fixation differs in Cerodontha incisa and other members of the subgenus Poemyza: Puparia inside the mine are tied up with silk instead of being glued to the cell tissue on the surface of the mine. The silk is loosely attached to the mine and the posterior spiracles, allowing the puparium to turn around.
HOST PLANTS
Avena sativa L. (Oats), Hordeum vulgare L. (barley), Secale cereale L. (rye), Triticum aestivum L. (wheat), Zea mays (maize) Also many wild grasses.
DISTRIBUTION
Widespread in Europe from northern Scandinavia to the Mediterranean; known from Moscow; Japan; Canada (Spencer, 1973).
ECONOMIC IMPORTANCE
The species regularly occurs on cereals but the populations are usually low. However, Pelov, 1974 considered the species at pest for maize. This reference indicates that Cerodontha incisa could be a potential pest species.