Regular surveys were made on the pollinating insect assemblages on seed onion fields of the Onion Research Unit of the Cereal Research Institute, Szeged near two settlements, Makó and Kiszombor in three consecutive years. During this period we collected 2263 wild bees, 24 specimens of non-Apoid Hymenopteraand 152 specimens of Brachycerous Diptera and analysed them considering different aspects. While processing the material 56 Apoid species, 11 other non-apoid Aculeate Hymenoptera and 21 Brachycerous Diptera species were registered. Pollination was done mainly by wild bees and also by honey bees. During these three years the Andrena flavipes Pz. (35.97%) was dominant species, while the Bombus terrestris (L.) (16,66%) and the Loasioglossum malachurum (K.) (13.74%) were subdominant species. Additional species were the Halictus simplex (Blüthg), Andrena carbonaria (L.), Andrena thoracica (F.), Lasioglossum calceatum (Scop), Bombus lapidarius (L.), Halictus quadricinctus (F.), Halictus maculatus Sm., Andrena tibialis (K.), Halictus veneticus Ebmer. Among Brachycerous Diptera Eristalis tenx L., Eristalis arbustourm L,. Stratiomys longicornis Scop and some Lucilia species were the most frequent visitors on onion inflorescence. During the experiment we observed that it was the Apoid Hymentoptera species that effectively carried out the pollination on the flowering onion fields. Our data present convincing proof of our previous findings that onion inflorescence does not have a range of specialised, determinate insect species visitors, although the long years of onion production traditions in the region of Makó would have been enough for some species to settle and spread. We observed that the most important in the pollination of the onion flower is the wild bee species with a wide plant spectrum and there are also some additional bumblebee and other insects species with a wide plant spectrum, depending on the place. Pollinating wild bee densities were 321.33 bee/ha in 2005, 858.60 bee/ha in 2006, 1837.34 bee/ha in 2007, on average of the three years 1005,76 bee/ha. Pollinating wild bee densities were decisively influenced by the temperature and the diversity of the bees was influenced by the existence of ruderal and direct close-to-natural areas around the flowering onion fields. All these factors resulted in the great density of seed setting wild bees on set soil in 2007. There is a positive correlation between the seed yield of the years and the density of the pollinating agents. In 2007 there was an outstanding seed set of 3243.06 kg/ha in the Makói Bronz type. The seed set quantity is mostly type-dependent, but the year and other ecological factors (like the soil and climate parameters as well as resistance characteristics) can also have an influence on it.

onion; wild bees; honeybees; flower visiting; diptera; flower visiting; pollen analysis

Presentation: oral