Japanese beetle

Japanese beetle

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Japanese beetles are small, colorful beetles living in North America, Europe, and Asia. They have a head and thorax of dark metallic green. These beetles have metallic coppery-brown outer wings covering most of the abdomen. These are not the wings that let the Japanese beetle fly, but they protect the functioning wings when they are not flying. These hardened wings are called elyptra. Around the back half of the abdomen, the Japanese beetle has small sections of white fuzz. There are six of these patches on each side of the abdomen. Both males and females have the same coloring and markings, therefore they look the same. There are a few other beetle that look somewhat like the Japanese beetle, but the markings I talked about above should let you distinguish them easily enough.

Size

Japanese beetles are not very large. The adults are usually between 0.4 and 0.5 inches (10-13 mm) long. The largest adults can be up to 3/4 inches (19 mm) long. They have a relatively flat body with not much of a domed shape. This makes them not very tall, but I have no measurements on how tall they actually are. These beetles can be a lot longer than they are wide. On average, the adults are just about 1/4 inch (6 mm) wide. Females are usually slightly larger than the males.

Diet

These beetles are considered huge pests, and you will soon know why. Japanese beetles eat almost any matter. Although they will eat weeds and even poison ivy, it is more common that they eat fruits, vegetables, flowers, or other crops. Farmers do not like these beetles because of how much damage they can cause to their crops. Some times a group of Japanese beetles will be able to eat all the leaves off a fruit tree in just 15 minutes! The young beetles, called grubs, are also destructive, as they eat the roots of plants underground.

Habitat and range

Japanese beetles are native to, well, Japan. They also live naturally in some other East Asian countries. Surprisingly, most of this animal’s range is outside of Asia! Not only do they live in Europe, but they have also been introduced to the eastern United States and Canada. The map below shows the places in the United States that Japanese beetles live.

Japanese beetle map US

It is kind of fuzzy, but the counties that are colored in with yellow are ones that are known to have an established population of Japanese beetles. It is thought that these bugs were first introduced into the United States in or before 1916 in a shipment of irises from Japan. After 1916, imports to the United States started being checked for possible invasive species. There are small populations of Japanese beetles in western North America that have likely hitched rides on vehicles or soil of garden plants.

These beetles are not very picky about their habitat. As long as they live in an area with a lot of foliage they will be fine.

Status and threats

No major conservation group has classified the status of the Japanese beetle. Despite this, it can be assumed that they would be ranked as Least Concern by the IUCN. This is because they are an invasive species. Obviously they are not underpopulated as they are overpopulated in many areas. In some places people are trying to kill Japanese beetles and keep them from invading more instead of trying to keep them alive and protecting their habitat. There are some threats to this beetle, but none that threaten its existence. There are some natural predators such as moles, skunks, shrews, and birds. Some insects like flies and wasps have actually been imported to the United States from Japan to control the Japanese beetle population! Insecticide used to protect plants from theses dangerous beetles is also a large threat. There are also a few diseases that kill off some of these pests.

Reproduction and young

The Japanese beetle’s life cycle begins when the adults emerge from their pupal state in mid-summer. They then congregate on suitable plants where they feed and mate. The same day she mates, the female will lay one to five eggs in the soil. Each female will mate multiple times throughout the summer, and she will lay from forty to sixty eggs during the year. Just two weeks after the eggs are laid, they hatch into the larva form of the Japanese beetle, often called grubs.

During the winter, the grubs hibernate in the soil to survive the cold. When the weather starts to warm up again, the larvae (plural of larva) re-emerge from the soil and soon turn into the pupal stage. They stay in this stage for up to twenty days before they turn into adults, completing the cycle. Japanese beetles only live for one year, so the adults never see beetles of a different generation.

Don’t forget to scroll down and comment your guess about what the next animal is!

Mystery animal

Sources:

Photo credits:

  • Japanese beetle – Futureman1199
  • Japanese beetle range US – Public domain
  • Mystery animal – H. Zell
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