Japanese Beetle

Quick Take

• A single shipment in 1916 unleashed this beauty on a continent. What was hiding inside?
• Even a beetle that devours almost anything refuses a few plants. Which ones make it back off?
• Dead beetles can work in your favor against living ones. How?
• Its dazzling looks hide a brutal underground life, and a long list of hunters is waiting.

Japanese beetles can be found in many places around the world, but they are only actually native to parts of Japan. Acting as foragers, these insects eat a broad diet of plant life (including fruits), so it is quite easy to make them feel at home. However, because they are invasive in the United States, Canada, and other parts of the world, people use pesticides and protective measures to reduce their populations.

5 Incredible Japanese Beetle Facts

• The eggs of a Japanese beetle are spherical and almost translucent. They also measure only 0.08 inches (2 mm) in diameter.
• This beetle was accidentally introduced to the United States in the early 1900s, imported with iris bulbs. They have since found homes around the world, including Canada and Italy.
• An individual female Japanese beetle will lay up to 60 eggs in her lifetime. When mating season occurs, the male will approach for mating. However, there is often more than one male fighting for the female’s attention.
• A Japanese beetle has four phases in its life cycle — egg, larva, pupa, and adult. They are a part of the scarab family.
• These beetles don’t live long, and they prefer to be in the sunlight. When night comes, the beetles hide in nests underground.

Species, Types, and Scientific Name

The scientific name of the Japanese beetle is Popillia japonica. “Popillia” is the scientific name of the genus of beetles. “Japonica,” on the other hand, is simply the modern Latin word for “Japanese.” Essentially, the name literally translates to “beetles of Japan,” despite their invasion into other parts of the world as a plant killer.

Currently, there are no recognized subspecies or other types of Japanese beetle.

Appearance: How to Identify Japanese Beetle

The colorful exoskeleton of the Japanese Beetle is the most notable feature, combining a vibrant green with a luminous copper hue. Its exoskeleton is hard, typically measuring between 0.4 and 0.5 inches (10 and 12 mm), and its bronze wing covers conceal strong wings. However, the largest Japanese beetles can get to 0.6 inches (15 mm) in length. The wing covers have their own name — elytra — and they conceal the wings while they aren’t in use.

When the Japanese beetle is still a larva, it is a white and soft grub. However, its head is still distinctly brown, and all three pairs of legs are visible. The metallic green doesn’t show up until they become adults.

Japanese beetles are not often found alone. They tend to group together, typically in swarms. Many countries have worked to eradicate the beetle, as it is highly destructive to plant life. To defend itself, the beetle primarily protects itself underground, but that doesn’t stop other insects (like spiders, ants, and beetles) and mammals (like cats, moles, and raccoons) from eating them. Sometimes, they are even hunted by wild birds (like robins and cardinals).

Habitat: Where to Find Japanese Beetle

Originally, the Japanese beetle is native to East Asia, but that’s hardly the only place it lives. In the United States, it has been an invasive species since 1916, and in Canada since 1939. Researchers believe that a shipment of iris bulbs contained the larvae of the beetles at the time, considering that imported goods did not go through the same inspections as they do now.

Part of the reason Japanese beetles are so adaptable is that they can find nourishment relatively easily. They’ll look for habitats that have plenty of foliage, which means that they survive just as well in areas with forests as they do in cities with small gardens.

Their life cycle takes them through many stages. When they are just eggs, they remain underground. After the male and female beetles mate, the female will go underground to lay the eggs. Typically, they become larvae (grubs) in about two weeks. Without proper control measures, the adult can damage plant life in the area.

Diet: What Do Japanese Beetles Eat?

The Japanese beetle only eats plants, but they will eat whatever plant life is available around them. They prefer to eat the leaves from trees and shrubs, but they also indulge in grass and nursery plants. Some adults will feed on fruit as well, like grapes, cherries, and peaches. Other typical foods include soybean, hibiscus, dahlia, horse chestnut, and sassafras.

The larva of the Japanese beetle exclusively goes after grass and similar plants. They also eat the roots that they find underground when they are in the grub stage of their life cycle.

Though the Japanese beetle has the ability to eat almost anything, there are still a few plants that are toxic to them — and they are toxic to humans as well. Larkspur and castor beans are quite poisonous, while white roses, marigolds, and lighter zinnias attract this beetle and can be used as trap plants.

Prevention: How to Get Rid of Japanese Beetles

As beautiful as these beetles can be, they cause a lot of damage wherever they end up. They often cause the biggest issue for gardeners, but there are many ways to eliminate them. If there are only a few, they can be hand-picked from leaves and placed into a cup of water with soap to eliminate them. While the beetles won’t harm you, some people prefer to use gloves.

Organic pesticides can help you to protect your plants from adults, and the pesticides can even be used inside traps. To gain control over the population before it booms, spray the soil with nematodes (which look like small worms) to go after the larvae. Unlike with other insects, the smell of dead Japanese beetles will deter other beetles as well, so containers of dead beetles can be placed near plants you want to protect (though traps should be emptied often for the same reason).