Data sheet water strider
Latin name:
Gerris
Trade name:
water strider
Origin:
Europe, North Africa, Siberia, China
Size (in cm:
10 to 20 cm
age expectation:
2 to 9 months
behavior/stocking
Location at the pond:
water surface
Dangerous?
No Webrunner, Gerris by webrunner, CC BY-SA 3.0
key data
Water striders are easy on the crosswise spread out, extremely long legs. They populate every garden pond in the warm season and are a good observation object for nature lovers. The water striders are among them bugs and have a proboscis, which they carry folded under their body.
With short strokes of the middle pair of legs, they rush across the surface of the water at high speed or glide smoothly over the water surface. If an insect falls into the water, they frantically pounce on it. The invertebrates never sink into the water. There are several types in Germany.
The most common species in our country are the Common Sandpiper Gerris lacustris and the Red-backed Sandpiper Gerris thoracicus. The animals have lived on earth for 100 million years; they were found as a fossil embedded in greaves. In England, the insects are aptly referred to as «water skaters».
Typical characteristics
All water strider species have a slender body covered with dense, water-repellent hairs. The short hairs on the phalanges prevent sinking on the surface and enable the animals to live on the water surface.
You can often see the insects cleaning themselves. Frequent cleaning gives the invertebrates the water-repellent properties of their dense hair coat.
head and legs
The head with the large eyes is triangularly pointed and has short, forward-pointing antennae. The proboscis folded under the head can be seen from the side, a feature of all bug species. Water striders have the triangular pronotum typical of all bugs.
It is noticeable that they are different long pair of legs. The animals seize their prey with their front, short extremities. The very long middle pair of legs is used for running fast on the water; the rear pair controls the direction of locomotion. The water strider can also perform short leaps and lunge at prey.
eyes and wings
«Water skaters» see their surroundings and their prey with well-developed compound eyes. The wings of the different species, sometimes also of the individuals of a species, show different stages of development. There are animals with stunted wings and insects with well-developed flight organs. The latter are able to cover short distances in slow hovering flight.
Occurrence in the pond
The Gerris species inhabit stagnant or slow-flowing water and always remain on the water surface. Water striders also occur on heavily polluted ponds and lakes. At newly created garden ponds belong to the pioneer species.
They always appear in larger numbers of individuals. Some water striders, such as B. the brook runner (Veliidae) live on flowing waters. The insects often hibernate at a greater distance from the water between moss and decaying plant parts. On land, the animals can only move clumsily by hopping.
Nutrition
Water striders feed purely carnivorous. They capture a variety of invertebrates that have fallen into the water and helplessly wriggle on the surface: mosquitoes, flies, ants, spiders, beetles and others. With the help of the vibrating sensory organs in their legs, they locate the movements of their prey on the water surface.
The victims are seized with the forefeet, pierced with a pointed proboscis and paralyzed by a poison. They suck the stunned prey. Often several «water skaters» fall at the same time on an insect that has had an accident. The large sea strider, Gerris paludum, is capable of overpowering dragonflies that have fallen into the water.
propagation
In the spring, the wintering animals wake up and mate. The females lay their eggs on objects and plants under the water surface. Small larvae hatch from the eggs. They undergo hemimetabolous development.
After each moult, the young animal looks more like the adult animal. Water strider show in Central Europe two generations per year. The spring generation dies after a few weeks or months, the summer generation overwinters and breeds the following year.
Other questions
Are water striders useful? Yes. They eat the annoying mosquitoes that have landed on the water. They also serve as food for fish and some bird species. Their presence livens up any garden pond and is an interesting sight.
Can water striders sting? Yes. Since their stinging apparatus is very thin, it cannot penetrate human skin, and their sting is neither painful nor life-threatening.