Family: Scarabaeidae Subfamily: Rutelinae Genus: Popillia Species: Popillia japonica Newman, 1838
Total body length 9.0–13.7 mm (0.35–0.54 in). Body oval-shaped. Color shining green, sometimes with reddish sheen; elytra shiny brownish. Clypeus slightly narrowed toward strongly recurved apex. Front claw toothed; male with toothed claw more robust than in female. Pronotum with dense punctation near anterior border; punctures distinct. Pygidium with 2 vaguely oval-shaped patches formed by dense whitish hairs (sometimes absent in worn specimens).
(Ritcher, 1966): Grub C-shaped, not hump-backed, cylindrical, whitish. Maxilla with galea and lacinia fused or nearly so. Frons lacking numerous punctures. Labrum asymmetrical. Claws sharply pointed. Dorsa of 9th and 10th abdominal segments not fused. Spiracles on 7th and 8th abdominal segments nearly equal in size. Segments 7–9 with dorsa with most of setae confined to 2 transverse bands. Palidia present, each palidium with 5-8 pali. Pali depressed or conical, never compressed. Venter of last abdominal segment with 14 or more preseptular hooked setae. Septula triangularly-shaped. Preseptular, hamate setae 35–57 in number. Lower anal lip with 19–29 long and short, straight setae.
Japan. This species is native to Japan, occurring on the four main islands of Honshu, Hokkaido, Kyushu, and Shikoku, but not the subtropical Ryuku Islands. This species is also known from the Russian Far East, specifically the islands of Sakhalin and Kunashir (Klein, 2008). Records from Korea and China are misidentifications of the similar four spotted beetle (Popillia quadriguttata) (Lee et al., 2007).
Popillia japonica feeds on a broad array of flowering plants. Over 300 plant species are recorded as hosts (Vittum et al., 1999). Amongst economically important plants, major hosts include maples (Acer spp.), asparagus (Asparagus officinalis), soybean (Glycine max), apples (Malus spp.), stone fruit including plums, peaches, etc. (Prunus spp.), rhubarb (Rheum x hybridum), roses (Rosa spp.), blackberry and raspberry (Rubus spp.), basswood (also known as linden or lime trees) (Tilia spp.), elms (Ulmus spp.), grapes (Vitis spp.), and corn (Zea mays) (Gyeltshen and Hodges, 2005). Secondary hosts include buckeyes (Aesculus spp.), hollyhocks (Althaea spp.), birches (Betula spp.), chestnuts Castanea spp.), rosemallows (Hibiscus spp.), American walnut (Juglans nigra), plane trees and sycamores (Platanus spp.), poplars (Populus spp.), willow (Salix spp.), common sassafras (Sassafras albidum), and American mountain ash (Sorbus americana) (Gyeltshen and Hodges, 2005). Larvae feed on the roots of many of the same plants that adults defoliate and also damage the roots of many turf grass species (Klein, 2008).
Because of its pest status, the lifecycle of the Popillia japonica is well known. In the eastern U.S., adults first emerge from pupation between May and July, and females begin laying eggs soon thereafter (Gyeltshen and Hodges, 2005). Females lay as many as 60 eggs (Klein, 2008) that are deposited 5.0–7.6 cm (2.0–3.0 in) deep in the soil, often under turf. Most larvae reach their final instar by September, burrowing as deep as 25.0 cm (10.0 in) to escape falling soil temperatures. Once temperatures fall below 10° C (50° F), grubs cease activity and overwintering occurs. Grubs resume feeding in the spring, and pupation takes place 4 to 6 weeks after feeding resumes. Pupation, which occurs near the soil surface, takes between 1 and 3 weeks. Males often emerge a few days before females (Gyeltshen and Hodges, 2005). Adult lifespan and activity are highly dependent upon local weather conditions. In the southern part of their range in the U.S., P. japonica adults often emerge in May (Gyeltshen and Hodges, 2005), while in Minnesota, adults usually emerge in mid-July (Krischik, 2011). Adults live between 30–45 days (Klein, 2008). Adults are most active during warm sunny weather, particularly around midday when they may be found feeding on exposed foliage (Gyeltshen and Hodges, 2005).
Severe. Though not a significant pest in its native Japan, this species is regarded as the single most destructive insect pest of lawns, gardens, and golf courses in the eastern U.S. (Klein, 2008). In 2000, the USDA estimated that $450 million were spent annually in the U.S. on Popillia japonica control (Potter and Held, 2002). Adults and larvae are both destructive pests. Adults defoliate a vast variety of plants, often congregating on a single plant, attracted by aggregating pheromones. Once a host plant is chosen, the beetles feed on foliage, stems, and flowers. Larvae feed upon grass roots and are serious turf pests (Krischik, 2011). In California, this species has established populations at least three times. Fortunately, subsequent eradication was successful (Potter and Held, 2002). In California, the beetle is regarded as a class A regulated pest, with a high likelihood of future introduction (Cosner, 2013). It is also listed as a quarantine pest in six other states, the Canadian province of British Columbia, and by the European and Mediterranean Plant Protection Organization (Potter and Held, 2002).
Recorded, not established. While not established in Hawaii, this species has been intercepted repeatedly in quarantine on Oahu (Nishida, 2002). The earliest of numerous records dates to 1925, when a single male was found on air cargo coming into Honolulu from Japan (Rainwater, 1963). Further interceptions took place in 1954, when 18 live adults were found over the course of a month on aircraft flying into Honolulu from East Asia. In 1955, eight specimens were intercepted on five different aircraft flying into Hickham Airforce Base from Tokyo, Japan (Hawaiian Entomological Society, 1954). In fact, between 1951 and 1959, 153 specimens were found by USDA inspectors (Hawaiian Entomological Society, 1961).
Not established or recorded. No records of this species on Guam exist (this may reflect a lack of documentation), though the closely related Popillia lewisi is established on the island (Marler and Moore, 2011).
Popillia japonica has been recorded hitchhiking on both air and marine cargo. The original introduction to the U.S. took place in the 1910's (Ritcher, 1966). It is believed that the initial introduction occured when an iris bulb shipment that hosted eggs or larvae was imported via a ship from Japan (Klein, 2008). Records in Hawaii indicate that this species has been intercepted in air cargo on multiple occasions (Rainwater, 1963). While parts of the western U.S. are suitable habitat, as illustrated by California introductions, it is unclear if Hawaii and Guam have optimal climates for P. japonica proliferation. Indeed, despite clear evidence that P. japonica has reached the islands, it has never established a self-sustaining population. In the eastern U.S., this species has never spread further south than Georgia, and it is absent from Florida (Gyeltshen and Hodges, 2005). In Japan, this beetle is most common on the colder, northern islands of Honshu and Hokkaido (Klein, 2008). This may be due to the seasonal lifecycle of P. japonica. Perhaps the larval overwintering period is required for successful pupation.
Popillia japonica is very similar to both Popillia lewisi, established on Guam, as well as the potential invader Popillia quadriguttata. These three species can be separated by examination of of the pronotal punctation (P. japonica with dense, distinct punctures near anterior border versus P. lewisi with sparse, small and indistinct punctures), pygidium (P. japonica with two vaguely oval-shaped patches of setae versus P. lewisi with crescent-shaped patches), clypeus (P. japonica with clypeus barely narrowing at apex, strongly recurved versus P. quadriguttata and P. lewisi with clypeus rounded, narrowing at apex, somewhat recurved), and often size (P. japonica at 9.0–13.7 mm [0.35–0.54 in] versus 11.0 mm [0.43 in] or less in P. quadriguttata and P. lewisi).
Popillia placatipennis Burmeister
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Popillia japonica mating and feeding by day, plant leaves with characteristic damage; photo by Lamba