Chromatomyia fuscula (Zetterstedt, 1838)
IMPORTANT CHARACTERS
Adults
Wing length: 2.3 - 2.6 mm. Very similar to Chromatomyia nigra and Chromatomyia obscuriceps (Hendel, 1935). Basal section of arista long, about as long as apical section. Frontal region and a part of the genae (cheeks) yellow or orange, occiput and posterior part of genae clear brown. Three main frontorbital bristles, of these only one inwards directed. One additional inwards directed small hair-like bristle is situated before the first frontorbital bristle (the reduced 4th). The second dc is located near the transverse suture. It may be difficult to interpret it as pre- or postsutural.
Females: Third antennal segment rounded.
Males: Sparse pubescence on the eyes (Spencer, 1973, Iwasaki, 1995, fig.). The genitalia are distinct especially between the three grass-mining Chromatomyia species fuscula, milii and nigra.
Immature stages
The anterior spiracles have each 8 bulbs on rather short stalks (fig. Spencer, 1973), shorter than in Chromatomyia nigra (fig. Spencer, 1973). The mine is linear whitish, with frass in distinct black pellets.
BIONOMICS
The life cycle of Norwegian populations in the vicinity of cultivated cereals and harvest grasses was studied in detail by Andersen, 1991: The flies emerge at the end of May and oviposit until July. The next generation can be detected from July until September of the same year. Several trials provided evidence that they do not oviposit in the same year. Hence, it must be concluded that they hibernate as imago and that the species is at least in Norway univoltine. Further studies confirmed that fuscula may be generally univoltine (Japan: Iwasaki, 1995; Canada: Andersen and McNeil, 1995). This is so far the only well corroborated case of adult hibernating in Agromyzidae. The temperature dependence of the development of egg, larvae and pupa are addressed in Andersen and Fugleberg, 1997.
HOST PLANTS
Avena sativa L., Hordeum vulgare L., Secale cereale L. and several wild and pasture grasses.
DISTRIBUTION
Japan, Europe (more common in the northern part), Canada, Greenland.
ECONOMIC IMPORTANCE
In Central Europe Chromatomyia fuscula normally occurs in small numbers below the threshold of economic significance whereas in northern Europe, higher infestation frequently result in yield loss (Spencer, 1973, Andersen, 1989).