No, do not underestimate gliding either. At first, four years ago, when I saw the first specimens ‘hanging quietly’ among the plants on my pollinator-friendly balcony, I thought: oh yes, you still have them. That gliding is characteristic of gliding. This will not happen automatically, even when the two wings (bees have four wings) are still moving at a speed of about 300 beats per second. Shooting is also very fast.
Either way, from the moment I photographed the first glider with my phone, I could not go back: this species group was also to be discovered. Especially when I photographed the other. For it had a completely different drawing than the first. The first was a mustache fly-orange, orange-yellow and black, the second a crescent-fly-fly, with cursed yellow crescents on its back. And then you have comma-like flies, with commas on their backs, tapeworm flies, flat feet, sooty noses, goblins, giants, heather dwarfs and more. There are about 330 species of sliding flies in the Netherlands, most of them in yellow-black colors. They are ‘sheep in wolf clothes’, says enthusiast Menno Reemer from EIS Knowledge Center Insects. They mimic, resembling wasps in color, to distract predators from their stingless defenselessness.
They are innocent vegetarians, the adult hoverflies, they feed on pollen and nectar, and are therefore also pollinators. Welcome guests to those who appreciate insects and plants. Also because many hoverflies in the larval stage are not vegetarians: Many species then feed on the aphids on the leaves of the plants where they grow. My balcony is a great place to be in that regard: lots of aphids. Nectar also for the adults. They live about three weeks and mate during that time. The females again lay eggs on aphid-rich leaves. New copies will appear within two weeks. This is how it continues until it gets crowded in the summer.
This spring started late, but I already saw a lot of slender triangular hoverflies and dot maze hoverflies. The mustache fly, the most common fly, I saw only this week. The mustache fly, so-called because you can see a mustache in the black markings between the yellow-orange bands on the back, is also one of the most beautiful hover flies. It is also known as the pajama glider or coca-cola glider.
In Spain, during my spring break, they flew in full. In theory, it could be that the southern hoverflies will be in the Netherlands later in the season, says Menno Reemer. Because mustache flies have a striking feature: they migrate en masse, they can travel hundreds of miles. An important part of the summer population of mustache flies in the Netherlands consists of migrants from the south.
There was bad news recently. At Veluwe, ecologist Aat Barendregt has since 1982 made an inventory of gliders on a fixed route. During that time, he noticed an 80 percent decrease in volume and almost a halving in the number of species. This is consistent with previous studies showing a significant decrease in insects. The causes are not officially known, but there is suspicion. Pesticide use in nearby farmland, for example, and the influence of nitrogen, for example, on the attractiveness of plants for different species of aphids. Striking: The mustache fly fly is one of the few species that survives. Maybe the migration keeps the level, but the mustache fly is also a generalist pure song, it flies on at least two hundred plant species for nectar and pollen.
Earlier in the week, I spotted on my balcony a mustache fluttering pupating on its backpack. Coincidence or not, but the next day I saw a first flying adult specimen. He could barely get in the newspaper.