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Yellow-billed beetles spend much of their lifetime in the water. They can bite at lightning speed and kill tadpoles, newts or smaller ornamental fish. The control of beetles and their larvae are difficult and basically not necessary. The yellow fire beetle is actually a beneficial insect, as it engages only in sick or dead fish and is thus responsible for the health in the pond.
- Latin name: Dytiscus marginalis
- belongs to the family of the floating beetles (Dytiscidae)
- other names: Common Gelbrand
- Origin: Europe, Asia and North America
- Body size: 27 to 35 mm
- Appearance: oval body, black-green body
- yellow border on pronotum and elytra
- Abdomen: yellow
- Males: black cover wings
- Female: green-brown winged leaves, longitudinally grooved (anterior two-thirds)
- Age: 3 to 5 years
Appearance and occurrence
The yellow sand beetle, botanically named Dytiscus marginalis, is one of the largest native swimming beetles. His body is wide oval and only moderately curved, mostly blackish brown with olive shimmer. While the male beetles have smooth wing lids, in the female specimens on the upper two-thirds of the wing lid distinct longitudinal grooves can be seen. Their names are the yellow fire beetles of the yellow framing of the pronotum and the wing lid. This yellow hem is well formed in both sexes. The largest species occurs in Northern, Central and Western Europe, smaller specimens are also native to Asia and North America.
habitatDytiscus marginalis has conquered several habitats. The most common part of life is spent in the water. The beetles are also able to crawl and fly quickly. Only these skills ensure their survival if they have to leave their waters in drought or lack of food. As a good flyer, the yellow fire beetle usually sets off at night to reach new waters. He often flies for miles and orients himself to water surfaces that reflect the moonlight.
The Common Gelbrand prefers smaller, plant-covered ponds and ponds with fresh water. Under the water surface, he clings to aquatic plants to ambush his prey. The beetles colonize mainly plant-rich shallow water zones of standing or very slowly flowing waters. Yellowbird beetles are among the fastest swimmers among the beetles. They spend much of their lives under water. To breathe, they swim to the water surface, emerge with the abdomen and pump air under the elytra. This will allow the beetle to stay underwater for a while.
proliferationAfter mating, the female lays between 100 and 500 eggs in the water. Partially the eggs are embedded in plant tissue. Until the complete development of the adult beetle, the larvae of the yellow sand beetle live in the water. The respiration of up to 80 mm long larvae takes place via the abdominal segment. Since they too need air to breathe, they mostly hang on the water surface. Pupation to the adult beetle takes place after about six weeks larval stage from June to July outside the water. Yellow sand beetles are between three and five years old and overwinter in the bottom mud of the ponds and pools where they live.
nutritionBoth adult yellow sand beetles and their larvae live predatory. They prefer to hunt in the early morning a variety of different prey that live in the water. Above all the larvae of the yellow fire beetles, which live up to the pupation exclusively in the water, belong to the dread robbers. Their jaws are transformed into impressive hollow daggers. The prey is pierced by these daggers and the digestive juices are pumped through them into the victim. The liquefied, predigested food is then sucked through the jaw canals. From the victim usually only the empty shell remains.
The food of the swimming beetles includes:
- other insects
- insect larvae
- dragonfly larvae
- little frogs
- small fish
Danger for fish
Although yellow-eared beetles have a reputation for being predators, there are usually no problems with fish in a garden pond.If the fish have enough space to swim, yellow sand beetles are not fast enough to catch healthy fish. In fact, the beetles live mainly on carrion, which they track down with their excellent sense of smell. The eyes are quite well developed, but play only a minor role in detecting the prey.
In some garden ponds, however, the actually harmless beetles have a devastating effect. For beneficial insects can also become pests if they occur in large numbers. Occasionally, the beetles can occur in masses in the water and then eat healthy fish. Usually, the yellow sand beetle and its larvae are only a danger if the ecosystem in the garden pond is ailing. This is usually because the conditions in the pond are not optimal:
- too dense plant growth
- bad water quality
- too high fish stock
fightOnce two or three yellow sand bugs appear in the pond, this is no reason to panic, but benefits the health of the biotope. However, if the beetles occur dozens and fall over the fish, one should not stand idly by. If you keep fish in the pond, you must refrain from using chemicals or biological agents, since in the worst case they mean the end of all pond inhabitants.
As a first measure, the larvae of the yellow sand beetle can be scavenged with a landing net. The yellow sand beetle larvae are six to eight inches long and are therefore easy to detect. Since the larvae hang with the rump on the water surface a lot of the time to breathe, they can easily be scavenged in the shallow water zone of the garden pond.
Change lighting conditions
Sunny shore sections are very important for the yellow sand beetle larvae. If the habitat is negatively altered, for example by shading, the larvae react very sensitively. In addition, it can be helpful to move the water surface. Currents created by pumps or a fountain in the pond, offer the larvae little opportunity to hang on the surface of the water to breathe.
The most important measure to prevent against all sorts of pests in the garden pond is to maintain the biological balance in the pond. This includes, among other things, that the fish are not overly fed. Excess fish food sinks to the bottom of the pond and pollutes the water. For newly created garden ponds, it may take a few years for the ecosystem to adapt to the pond. A well-functioning biotope usually manages to maintain its biological balance. Meanwhile, the following measures can help:
- pruning strongly proliferating pond plants
- Remove dead plant parts regularly
- Prevent algae growth (possibly scoop with landing net)
- regularly suck off about one third of the pond sludge