YEAR-ROUND PITFALL TRAPPING OF MILLIPEDES IN MAINLY OPEN GRASSLAND INBELGIUM (DIPLOPODA)

From September 1993 to September 1994 a programme of continuous pitfal l trapping was undertaken by the Belgian Royal Institute of Natural Sc ience on the Montagne St. Pierre. This hill is situated south of Maast richt on the west bank of the River Meuse, partly in the Netherlands a nd partly in Belgium. The study site is calcareous, and lies to the we st of the village of Lanaye in Belgium, very close to the boundary of different biogeographical zones. Trapping was undertaken in five areas of open grassland and one area of former grassland substantially inva ded by bushes in a successional stage towards deciduous woodland. The traps were emptied every two weeks. Seventeen species of diplopods wer e captured, twelve of which were julids. Julids comprised 93% of the i ndividuals caught (4340 out of 4643 animals); the species Cylindroiulu s caeruleocinctus (Wood, 1864) was predominant (3815 individuals, repr esenting 82% of the captures). Activity was greatest in late winter an d spring, with a subsidiary peak in autumn, and correlated reasonably well with minimum temperature from the autumn until the spring. Few in dividuals were captured during the summer. Some species were caught on ly during limited periods of the year. In Cylindroiulus caeruleocinctu s the proportions of males and females obtained in the traps varied co nsiderably from season to season; there was a marked predominance of m ales in the traps during the winter.