Family: Scarabaeidae Subfamily: Rutelinae Genus: Popillia Species: Popillia lewisi Arrow, 1913
Total body length 8.4–10.3 mm (0.33–0.41 in). Body oval-shaped. Color shining green, sometimes with reddish sheen; elytra shiny tan to brown. Clypeus rounded with apex somewhat recurved; narrowed toward apex. Front claw toothed, male with toothed claw more robust than in female. Pronotum with sparse punctation near anterior border; punctures small, indistinct. Pygidium with 2 crescent-shaped patches formed by dense, whitish setae (setae often lost in older specimens).
Undescribed. For Popillia spp. (Ritcher, 1966): Grub C-shaped, not hump-backed, cylindrical, whitish. Maxilla with galea and lacinia fused or nearly so. Frons sparsely punctate. Labrum asymmetrical. Claws sharply pointed. Spiracles on 7th and 8th abdominal segments nearly equal in size. Dorsa of 9th and 10th abdominal segments not fused. Septula shaped like an equilateral triangle, palidia strongly diverging posteriorly; each palidium with 5–7 (rarely 8) long, ensiform pali. Venter of last abdominal segment with 14 or more preseptular, hooked setae.
Japan. In Japan, this species is known from Okinawa and the Ryuku Islands (Schreiner and Nafus, 1986).
Though little information is available regarding the feeding habits of this species, it is likely that preferences are similar to the well-known Japanese beetle (Popillia japonica). Adult Japanese beetles (P. japonica) are generalists, feeding on the foliage and flowers of a broad range of plants, while larvae feed on grass roots (Krischik, 2011).
Adults may be found during the day feeding on plant foliage. Based on specimens examined at the University of Guam, it appears that the adults are active throughout the year. Natural history and larvae are undescribed.
Significant. In Guam, this species is a significant pest of "ornamental plants" (Marler and Moore, 2011), although details are scarce. The related Popillia japonica damages plants as both an adult and larva. Adults of P. japonica damage plants in mass, attracted to aggregating pheromones and feed on both foliage and flowers. Larvae feed upon grass roots and can be serious turf pests (Krischik, 2011). In California, P. lewisi is regarded as a class A regulated pest, with a high likelihood of introduction (Cosner, 2013).
Recorded, not established. While not established in Hawaii, this species has been intercepted in quarantine on Oahu (Nishida, 2002). Intercepted specimens were found in 1991 aboard U.S. Air Force aircraft flying in from Andersen Air Force Base on Guam (Moore, 2012).
Established. This species is established on Guam, having first arrived in 1985 (Schreiner and Nafus, 1986). It seems likely that this early population came in on U.S. Air Force aircraft, flying from bases on Okinawa (Marler and Moore, 2011). Indeed, for many years P. lewisi was confined to the vicinity of the docking bay of Andersen Air Force Base, persisting there despite some early eradication efforts (Schreiner and Nafus, 1986). Since then, this beetle has spread to the remainder of Guam, becoming a serious pest (Marler and Moore, 2011).
In both Hawaii and Guam, it appears that military air cargo was the primary mode of transportation for this species (Moore, 2012). It is possible that this species could spread to California or Florida via similar means. Further, it is reasonable to expect that adult beetles could hitchhike on nursery plants, or larvae could be transported in commercial turf. This species should be regarded as having a high likelihood of spreading to Hawaii.
This species is easily confused with two very similar potential invaders: Popillia quadriguttata and Popillia japonica. These species are separated by examination of pronotal punctation (P. lewisi with sparse, small and indistinct punctures near anterior border versus P. japonica and P. quadriguttata with dense, distinct punctures near anterior border), clypeus (P. lewisi with clypeus narrowing at apex and somewhat recurved versus P. japonica with the clypeus barely narrowing at the apex and strongly recurved), the pygidium (P. lewisi with 2 crescent-shaped patches of white setae versus P. japonica and P. quadriguttata with patches vaguely oval-shaped), and often by size (P. lewisi at 8.4–10.3 mm [0.3–0.4 in] versus P. japonica at 9.0–13.7 mm [0.35–0.54 in]).
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