De roodrandzandbij Andrena rosae in de Zuid-Hollandse Biesbosch (Hymenoptera: Apoidea: Andrenidae).

Andrena rosae in the Zuid-Hollandse Biesbosch (Hymenoptera: Apoidea: Andrenidae) Andrena rosae is a fairly large, black and red mining bee. It has declined dramatically in the 20th century in northwestern Europe. In the Netherlands the species only survived in and around the Biesbosch, at the confluence of the rivers Maas and Rijn. In 2005 a research was performed to establish the distribution pattern within the northern part of the Biesbosch (province of Zuid- Holland). Furthermore, attention was paid to nest locations and pollen gathering. The species proved to be quite common throughout the study area. In spring, nests were found on the southern slopes of the dikes. Surprisingly, no nests could be found during the summer months. Near the nests unusually large specimens of Nomada fabriciana were found: these might possibly be parasites of A. rosae. In spring, female A. rosae where seen only on Salix and Prunus spinosa. Pollen analysis indicated that pollen had only been collected on Salix. In summer, females were frequently found on Heracleum sphondylium, Angelica sylvestris, Eryngium campestre and occasionally (and surprisingly) also on Filipendula ulmaria. Pollen analysis showed that the bees indeed collected pollen on all of these plants. German authors (e.g. Westrich 1989) state that A. rosae occurs only in summer and that the spring specimens belong to another species, A. stragulata (synonym A. eximia). Presently, this matter is being studied by analysing the dna of Dutch specimens. Details of this dna-analysis will be published separately.