Mighty dunes and small pits with predatory ant lions await those who enter the Ullahau nature reserve.
Ullahau is a large, horseshoe-shaped sand dune that is part of the large flying sand area that covers almost the entire Avanäset. At most, the dune rises just over 15 meters above the surroundings. The Ullahau dune probably began to form during the first half of the 18th century, probably as a result of excessive deforestation and grazing. On its way south, the sand suffocated large areas of forest, and some arable land was also covered with sand. In order to stop the flight of sand, intensive planting work was started at the beginning of the 20th century, and only a few decades later, the migration of the dunes had largely been stopped. Today, Ullahau is largely overgrown with forest – mainly pine forest – and the open sand areas cover a total of only about 40 hectares.
The flora in Ullahau is consistently species-poor. In the open sandy areas, the vegetation is dominated by lichens and mosses as well as grass and semi-grass. Here and there between the tufts of grass are single specimens of flock fibla or monk. Inside the forest, the ground is often covered with heather or blueberry rice.
Hymenopteran and ant lion
Ullahau’s open sandy soils constitute a very special habitat with an extreme microclimate in many respects. This puts its mark on, among other things, the area’s insect fauna, which is unusually rich in heat-demanding dryland species. These include a number of species of Aculeata, some of which are extremely rare in our country. In Ullahau you can also meet all three of our Swedish species of ant lion dragonflies and especially their larvae, the ant lion. The ant lion is buried in the sand at the bottom of a funnel-shaped trap. When an ant or other small insect happens to fall into the pit, the ant lion splashes sand on its victim so that it slides further and further down to the bottom of the pit. Finally, the ant lion grabs its prey with its long jagged jaws and pulls it down into the sand.