Forest ranger Frans Kapteijns shares his knowledge of nature every week. Anyone can submit questions via [email protected]. This time, Frans pays attention to, among other things, inverted, somewhat pear-shaped, bare and hollow galls, a yellow-edged water beetle that now has a new name – ordinary yellow-edged – and to a kind of white bag on a tree. Part one of this Stuifmail was already published on Saturday.
What is this growing here on a leaf?
Mieke van Schijndel thought she saw a birch seedling, but it turns out not to be a birch seedling: it is an elm. She also saw something on the tray and wondered what it was.
The funny thing is that shortly after her message I received a message from Elly van den Reek. She also had an elm leaf with something on it. I think the strange thing on Mieke and Elly’s elm leaves are elm grass aphid galls. The elm grass aphid galls are caused by elm grass aphids. These animals are very small and grow to a maximum of two millimeters. So they are difficult to find, but they are active from May to September.
However, the galls are very noticeable: they grow to about 15 millimeters in height and look like inverted, slightly pear-shaped, bare and hollow structures. At first they are green, later they turn yellow and eventually dry to a reddish-brown color.
The elm grass aphid galls are more noticeable, because they are about 15 millimeters in size and ultimately look like inverted, slightly pear-shaped, bare and hollow galls. At first they are green, later yellow and eventually dry to a reddish-brown color.
The galls arise on the top of the elm leaves. Often part of the leaf around the gall turns yellow and becomes slightly deformed. There is a hairy opening at the bottom that closes later. When the aphids are fully grown, the gall ruptures and they move to the roots of grass under the tree, usually nursery grass.
What is moving in my pond?
John Selten saw something moving in his pond one morning and immediately thought it was a beetle. He sent me a photo and asked if I knew which beetle it was.
I think it is a yellow-edged water beetle, which now has a new name: common yellow-edged. The name yellow-edged water predator beetle is also used. This common yellow-edge beetle belongs to the family of water predatory beetles and, with a length of 3.5 centimeters, is one of the largest beetles in the Netherlands.
The menu of these voracious predators mainly includes insect larvae, but also water spiders, dead animals and small fish. They can fly very well, just like ladybugs. They often fly at night to a new pool, puddle or pond. Leaving such a body of water is therefore mainly done at night, but also in windless and rainy weather. This mainly happens in late summer and early autumn. The reason for this is that a new generation of water predatory beetles is emerging from their pupae, but also that a pool of water can threaten to dry up, causing a food shortage.
Seeing a common pipistrelle bat on the street, what’s going on?
Jos Cleijsen went to put his PMD container on the street when he saw something lying there. When he looked closer, he saw that it was an injured bat.
From the looks of it, it is indeed a bat and I believe it is a common pipistrelle bat. There is something wrong with one of the wings, but unfortunately I don’t know if help has arrived for the injured bat. Common pipistrelle bats, with a maximum length of fifty millimeters, are one of the smallest bat species in Europe.
The menu of these bats mainly includes small insects such as mosquitoes, sedges, moths and lacewings. In principle, they catch about three hundred of these prey animals in one night. They come out about thirty minutes after sunset and continue hunting for eight hours straight. Then they return to their sleeping places. Especially in the summer, they sleep during the day in cavity walls, in fascias, under roof tiles and behind wooden cladding. In addition, there are also maternity colonies in the summer, where the females sit with their young.
Natural enemies of the common pipistrelle bat are domestic cats, owls, birds of prey and corvids. Barn owls and tawny owls hunt various bats and diurnal birds of prey can still do so at dusk. The most important non-natural enemy is the domestic cat. Weak bats are often the victims, but sometimes, when domestic cats discover a maternity colony, all the animals are eaten. Terrible.
What kind of white bag is that on a tree?
Petra Keijsers saw a kind of white bag on her tree and wondered whether it was a fungus or an insect’s nest. It’s not. What is on the tree at Petra is called a silver tree cushion. These are not molds or fungi, but myxomycetes. They belong to the mycetozoan kingdom and not to the fungal kingdom. In the Netherlands we have translated myxomycetes to the word slime mold, although that is a somewhat confusing name.
Silver tree cushions are cushion-shaped and initially have a silver sheen, hence the name. They can grow up to ten centimeters in size. The contents are silvery white at first, but later become chocolate brown. When that stage is reached, the membrane tears open and the spores spread with the help of rain and wind.
About 300 species of myxomycetes occur in the Netherlands and almost 1,000 worldwide. Most develop on dead and living wood, such as branches, trunks and bark, but also on leaves, stems and moss.
Beautiful photos section
The Munnikenland area is located in the far western part of the Bommelerwaard. There the photographer found this beautiful spoonbill and took a beautiful image (see above).
Nature tip
On Saturday, June 6 from half past two to four in the afternoon you can discover nature in the Biesbosch with a guide. During the walk along the Griend Museum Path, the guide will talk about the variety of plants and animals and show how biodiversity affects our daily lives.
More information:
- This tour is not suitable for (young) children
- The walk costs eleven euros per person
- You can do the walk here books
