| Resumo: |
Sphecodes majalis, a new bee species for the Netherlands (Hymenoptera: Apidae) A population of Sphecodes majalis was found on a limestone grassland near Maastricht (Limburg). On several occasions more than 10 female and several male specimen were observed. Sphecodes majalis is a parasite of Lasioglossum pallens, which was recorded for the first time in the Netherlands in 1997. Since then L. pallens has become well established in the southern part of the province of Limburg. At the locality where S. majalis was found, L. pallens occurs in large numbers. In April many dozens of males swarm along the woodland edges. The less conspicuous and solitary females mainly nest in dense Festuca rubra swards with a thick litter layer, rather than in the open Mesobromion plant community. At these nesting sites the largest numbers of S. majalis were observed. As S. majalis was recently found in nearby Belgium, its appearance in the Netherlands was expected. Yet the Belgian-Dutch occurrence seems to be situated way outside the known distribution area, the nearest sites being located in southern Germany and western Switzerland. In well-studied Germany S. majalis is long known from one locality in Bavaria without any sign of expansion. All Swiss records however are made since 1970. It is therefore hypothesized that the recent expansion has followed a south-western route, i.e. through France, where the knowledge of the distribution of bees is rather patchy.
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