Flying insects underwater : caddisflies, stoneflies, mayflies, midges and other flies, water beetles and dragonflies.

CADDISFLIES (TRICHOPTERA)

MAYFLIES (EPHEMEROPTERA)

The two developmental stages of the mayfly. On the left the larva, recognizable by the 3 long body appendages, the gill leaves are on the side of the body. On the right the imago recognizable also by the 3 long appendages and the straight erect pairs of wings in the resting state.

The mayflies have nothing to do with the real flies. The larvae live in the water and are clearly recognizable by their 3 long (difference to stoneflies!), thread-like body appendages. In flowing waters they usually burrow into the mud of the water bottom and actively filter the water for food (detritus). In still waters, swimming mayfly larvae also occur. They can be observed sitting on leaves of aquatic plants, where they also find the algal cover as food. They are often yellow with brown markings and are found in clear oxygen-rich waters. The larvae are often only 8 to 23 mm long. Sometimes their skin is found on surrounding shore plants. This is because before their last molt, the larvae usually climb ashore. There, a preliminary stage of the adult mayflies (subimago) hatches within a minute. The mayflies are the only species that then complete another molt (imago). The adult mayflies live only a few hours or usually two to three days, depending on the species. During this time they are looking for a mating partner and do not eat anything.

STONEFLIES (PLECOPTERA)

MOSQUITOES AND TRUE FLIES (DIPTERA)

Most mosquito and fly larvae as in the illustration above can survive well in nutrient-rich waters, but not species of the blackfly larva (Simuliidae) Illustration and photo below. It is an exception because it helps purify the water with its fan-like bristles with which it filters food from the water. It is only half an inch in size and difficult to spot. It crawls along water plants like a caterpillar and attaches itself to leaves with its adhesive disc. It can be found only in flowing waters, it lives in oxygen-rich streams and rivers of the Ösling and Gutland. Eggs are laid in running water, and the larvae attach themselves to rocks. Breeding success is highly sensitive to water pollution

Mosquitoes (Culicidae)

Mosquitoes have no demands on their water bodies and colonize any still water, including small bodies of water such as puddles or rain barrels. They hang upside down under the surface of the water and scour the water for food particles. Their breathing tube is in contact with the water surface. Mosquito larvae are usually white or yellowish, about 10mm long and have a rather large head with 2 eyes. The larva of the invasive tiger mosquito also looks like this and can hardly be distinguished from the native species. The larvae pupate before the adult mosquito hatches from them, at this stage the mosquito pupa looks different again.
The female adult mosquitoes are bloodsuckers because they need the blood to mature their eggs. The males, on the other hand, feed on flower nectar and dance in swarms on the shore.

Chironomids (Chironomidae)

Chironomids (nonbiting midges or lake flies) larvae also have an elongated worm-like shape and can be different colors. They live differently some live freely in the water and are up to 2 cm in size and white, yellowish, green or brown-gray. Andre larvae live in the mud and are light to dark red. They do not need a breathing tube, as they absorb oxygen from the water through their skin. The red forms in particular can still survive in eutrophic waters with little oxygen, as their red pigment helps them still draw residual oxygen from the water. The adult mosquitoes do not bite, even though they look very similar to mosquitoes.

Hover flies (Syrphidae)

Larvae of hover flies live in nutrient-rich, stagnant or slow-flowing waters. They also tolerate heavy pollution and are also found in very small bodies of water such as septic tanks, sewage ponds or brackish water puddles. Such as the larvae of the common drone fly (Eristalis tenax), also called "rat-tailed maggot", which is actually the long breathing tube of the larvae. They live in the mud or sometimes float on the water surface and are relatively large at 10-25 mm. The adult hoverfly is a flower visitor.

BEETLE (COLEOPTERA)

Most beetle species whose larvae and beetles live in water belong to the groups of water beetles (Dytiscidae) or true water beetles (Hydrophilidae). The forms of the beetle larvae are very diverse, which is why it is often not possible to identify them immediately as beetle larvae (see schematic illustration above). Larvae of the water beetles and the beetles themselves are both predatory and feed on other small aquatic animals, species of the water beetle group also feed on algae and aquatic plants. Water beetles are usually very small and rarely grow over 1 cm in size. Exceptions are the conspicuous animals living in lakes and ponds, such as the great diving beetle Dytiscus marginalis, the broad-edged beetle Dytiscus latissimus or the great silver water beetle Hydrophilus piceus.

Species of hooked beetles (Elmidae) are most common in Luxembourg waters. They need a lot of dissolved oxygen in the water for their complex underwater respiratory supply. Thus, they prefer cold, flowing, oxygen-rich water and are thus found in streams or lakes with a lot of water movement. All cleanliness characteristics for bodies of water. They use their hooks on the ends of their legs to claw at aquatic plants, stones or leaves. They are tiny, with a body size of up to 2.5mm, and even their larvae, which look similar to a brown elongated isopod, are only a bit larger (3-4 mm). Therefore, they are not so easy to spot. The beetles and the larvae eat dead plant material and algae from e.g. stones. Hooked beetles are not swimmers, they walk slowly underwater.

Marked as other animal?

BUGS: Semiaquatic bugs (Gerromorpha) and water bugs (Nepomorpha)

Bugs can also look so similar to beetles, you can distinguish them by some features:

• Bugs have sucking proboscis, beetles have biting and chewing tools.
• You can't see wings in beetles, they are mostly hidden under the carapace. In bugs you can see their wings, which they have folded over their back.
• Most species of bugs are predators, feeding on any insect that overpowers them. They sit on aquatic plants, in mud, or on old leaves where they lie in wait for food. Even small fish and tadpoles are eaten.

DRAGONFLIES (ODONATA)

There are 2 major groups of dragonflies, the damselflies (left) and the true dragonflies (right). All larvae live in water but look different. The larvae of the damselflies have 3 leaf-like appendages on the abdomen, these are their gill leaves. Damselflies are slender and elongated in shape and usually have a brown-yellow to gray coloration. The larvae of the true dragonflies do not have tail gill leaves, their gills are hidden in the abdomen. They have more of an oval shaped body and also have a "catching mask" on their head that allows them to dart forward to grab their prey.

All dragonfly larvae are hunters and lurk among plants or almost completely hidden in the mud for other aquatic insects, worms or even tadpoles. Before its final molt to adult dragonfly (imago), the larva climbs out of the water and clings to riparian plants. At the back, its skin bursts open and a soft, pale dragonfly squeezes out. From hatching to the first flight of the dragonfly usually takes several hours, the skin (exuvia) remains on the plants and can be discovered by nature observers.

The development of the White-legged damselfly (Platycnemis pennipes) and the Beautiful demoiselle (Calopteryx virgo) is more likely in clean waters with sufficient plant growth and structure. Natural river courses with many marginal areas, with aquatic and riparian plants are optimal for dragonflies. One can only speak of indirect bioindicators for good or near-natural water quality. The Beautiful demoiselle can be found in some river courses of the Ösling, it prefers still or slow-flowing waters. Most of the flying dragonflies can be observed between mid-May and mid-September.