The Japanese beetle (Popillia japonica) is a species of scarab beetle. The adult measures 15 mm (0.6 in) in length and 10 mm (0.4 in) in width, has iridescent copper-colored elytra, and a green thorax and head. Due to natural predators, the Japanese beetle is not considered a pest in Japan, but in North America and some regions of Europe, it is a noted pest to roughly 300 species of plants. Some of these plants include rose bushes, grapes, hops, canna, crape myrtles, birch trees, linden trees, and others.
The adult beetles damage plants by skeletonizing the foliage (i.e., consuming only the material between a leaf's veins) as well as, at times, feeding on a plant's fruit. The subterranean larvae feed on the roots of grasses.
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TerrestrialTerrestrial animals are animals that live predominantly or entirely on land (e.g., cats, ants, snails), as compared with aquatic animals, which liv...
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OviparousOviparous animals are female animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive...
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starts withAdult P. japonica measure 15 mm (0.6 in) in length and 10 mm (0.4 in) in width, with iridescent copper-colored elytra and green thorax and head. A row of white tufts (spots) of hair project from under the wing covers on each side of the body. Males are slightly smaller than females. Grubs are white and lie in curled positions. A mature grub is roughly 1 inch (2.5 cm) long.
Popillia japonica is native to Japan, but is an invasive species in North America and Europe.
The first written evidence of the insect appearing within the United States was in 1916 in a nursery near Riverton, New Jersey. The beetle larvae are thought to have entered the United States in a shipment of iris bulbs prior to 1912, when inspections of commodities entering the country began. As of 2015, just nine western states of the United States were considered free of Japanese beetles. Beetles have been detected in airports on the west coast of the United States since the 1940s. Only three were found in Washington State, USA, in 2020, but from late June to September 3, 2021, there were over 20,000 found in Grandview alone.
The first Japanese beetle found in Canada was inadvertently brought by tourists to Yarmouth, Nova Scotia, by ferry from Maine in 1939. During the same year, three additional adults were captured at Yarmouth and three at Lacolle in southern Quebec.
Japanese beetles have been found on the islands of the Azores since the 1970s. In 2014, the first population in mainland Europe was discovered near Milan, Italy. In 2017, the pest was detected in nearby Ticino, Switzerland. In 2023, the first population north of the Alps was detected in Kloten near Zürich, Switzerland.
Eggs are laid individually or in small clusters near the soil surface. Within approximately two weeks, the ova hatch, then the larvae feed on fine roots and other organic material. As the larvae mature, they become c-shaped grubs, which consume progressively coarser roots and may do economic damage to pasture and turf at this time.
Larvae hibernate in small cells in the soil, emerging in the spring when soil temperatures rise again. Within 4–6 weeks of breaking hibernation, the larvae will pupate. Most of the beetle's life is spent as a larva, with only 30–45 days spent as an imago. Adults feed on leaf material above ground, using pheromones to attract other beetles and overwhelm plants, skeletonizing leaves from the top of the plant downward. The aggregation of beetles will alternate daily between mating, feeding, and ovipositing. An adult female may lay as many as 40–60 ova in her lifetime.
Throughout the majority of the Japanese beetle's range, its life cycle takes one full year; however, in the extreme northern parts of its range, as well as high-altitude zones as found in its native Japan, development may take two years.
