The butterfly-rich dunes of Zuid-Kennemerland
Joop Mourik en Mariek Eggenkamp
The coastal dunes of Zuid-Kennemerland form one of the most butterfly-rich areas in the Netherlands. Over the last twelve years, detailed inventories of the 7,200 hectares by about a hundred volunteers have resulted in more than 500,000 records. These data reveal not only the detailed distribution of a certain species, but also how numbers have changed. Of the 37 species sighted, 26 complete their life-cycle in the dunes. For some, the dunes are the last foothold in the Netherlands; six residents are on the Red List, but two are common here, and three others quite widespread. There is a large variety of habitats: seawards, open dunes, either with a cover of lichens or sparse grass, or Hippophae rhamnoides scrub or rough grass, midway, a scrub-rich savannah landscape, and on the landward edge, dry woodland giving way to a park landscape with tall trees. The authors not only discuss distributions and trends, but also give interesting details on certain species. All this and more is to be found in their book.
Farming for meat and butterflies?Michiel Wallis de Vries
In the framework of the European FORBIOBEN project, a four-year experiment was done on the response of butterflies, grasshoppers and animals of other taxa to different grazing regimes at sites in the United Kingdom, Germany, France and northern Italy. The effects of moderate and low stocking rates were compared, as well as those of commercial or traditional breeds. Sheep were used in Italy and cattle elsewhere. For butterflies and grasshoppers, the difference between the moderate and extensive grazing regimes was substantial, with consistent effects between the various sites: at the lower stocking rate, species richness and the abundance of individuals were the highest. However, the breed of livestock used had no significant effect. These results applied to both the species associated with short vegetation and those of tall vegetation. Extensive grazing therefore proved to have a good potential for enhancing the diversity of insects in a cultural landscape.
The biology of the White ProminentJeroen Voogd en Dick Groenendijk
The white prominent (Leucodonta bicoloria) lives in the topmost branches of Betula trees; few caterpillars have thus been found, also because they clasp tightly onto the leaves. As the freshly emerged moths are usually found in the litter layer, pupation supposedly takes place there. To elucidate more of the moths life history, two female moths were kept on fresh birch twigs in a spacious cage, where they laid small green eggs on the underside of the leaves. During the observations, the caterpillars mostly change colour when ready to pupate. These full-grown caterpillars, eat 'rings' of bark away form the twigs they are feeding on, and so cause the leaves to wilt. It was
shown during the rearing experiments that the caterpillars fall onto the ground between spun wilted leaves and enter the last moult into the chrysalis stage on the ground. This shows that when raising caterpillars in order to answer questions on a species' biology, conditions should be kept as natural as possible.
Laatste wijziging: 27 oktober 2009