Distribution and population densities of stemboring fly larvae (Diptera) and their parasitoids in Danish farmland
1994
Brunberg Nielsen, L. (Aarhus Univ. (Denmark). Inst. of Biological Sciences. Dept. of Zoology)
Grass samples from various field types in Denmark were dissected for stemboring fly larvae in order to estimate population densities. Oscinella species were predominant. The results support the assumption that Oscinella vastator and Oscinella pusilla are stationary species building up high population densities in perennial established fields, whereas Oscinella frit is highly expansive primarily invading annual crops. From an Oscinella frit aberrant type larval type four species emerged: Oscinella hortensis, O. nigerrima, O. pusilla and an O. frit resembling fly. O. hortensis was primarily found in stems of Festuca rubra and Festuca ovina, but also of Deschampsia flexuosa. Of the stemboring larvae 15.5 % were parasitized by hymenopterous parasitoids, the wingless braconid Chasmodon apterus was responsible for 67.6 % of the parasitism
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