I’m particularly fond of hiking in early spring. It’s not for the spring weather, which is often raw and windy, or for spring flowers, which aren’t particularly abundant in the bush. No, it’s for the lack of German wasps.
Much of the forest we hike through is dominated by beech (not the northern beech, but several species of Nothofagus). Beech is host to a fascinating ecosystem which has been invaded by non-native wasps.
Throughout much of its range, beech is infested by scale insects. The scales live in the bark of the trees, feeding on sap. Because sap is low in nutrients and high in sugar, the insects need to excrete the extra sugar. Each insect has a long anal tube through which it ‘pees’ concentrated sugar water called honeydew.
Drops of honeydew form on the tips of the anal tubes and fall to the ground, tree, trunk, and branches around the insects. The entire area ends up coated in sticky sugar.
Sooty mould grows on the sugar coated surfaces, turning trees and forest floor black, and giving the beech forest a distinctive smell. The sooty mould is eaten by a variety of insects, including moths and beetles.
But not all of the honeydew simply drops to the ground. Native birds and insects (and hikers) drink the drops of water on the tips of the scales’ anal tubes. For wildlife, honeydew is an important winter food, when flower nectar is scarce.
German wasps enjoy honeydew, too, but only in the summer.
By mid-summer, the beech forest hums with the sound of millions of wasps collecting honeydew. For me—allergic to wasp stings—it means a hike requires constant vigilance lest I grab a tree trunk for balance and end up in anaphylactic shock. But in springtime, the wasps aren’t yet out and about, and I can enjoy the sticky smell of the beech ecosystem without worry.