coconut rhinoceros beetle, coconut beetle
Family: Scarabaeidae Subfamily: Dynastinae Genus: Oryctes Species: Oryctes rhinoceros (Linnaeus, 1758)
DNA Barcode available: specimen information
Total body length 40.0–60.0 mm (1.57–2.36 in). Body shape elongate, slightly cylindrical. Color dark brown to black. Ocular canthus not produced. Head of male with long, slightly curved horn ending in single point; female with horn present but usually reduced. Pronotum of both sexes without horns, but with broad, sculpted depression. Pygidium of female with dense red-brown setae, setae much more sparse in male.
(Bedford, 1974): When alive, larvae are firm to the touch and crawl on their venter. Similar-sized Protaetia larvae feel distinctly "squishy" and crawl on their backs with their legs up. Grub C-shaped, not hump-backed, cylindrical, and cream-colored. Maxilla with galea and lacinia fused or nearly so. Lacinia of maxilla with 3 well-developed unci. Maxillary stridulatory teeth truncate. Head with numerous rounded pits, most with a tiny seta. Respiratory plate with 40–80 (sometimes more) round or oblong punctures. Legs 4-segmented. First thoracic segment with single, long seta and 3–8 shorter setae; shorter than width of sclerite. Thoracic spiracles larger than abdominal spiracles. Distinct anal ring on terminal segment. Plegmatia absent.
Southeastern Asia. This species has a wide distribution across tropical and subtropical southeastern Asia, ranging from India and Pakistan, through Indochina, east to Okinawa, the Philippines, and Indonesia. The species has spread widely beyond its native range and can now be found in the Bismarck Archipelago, Palau, Reunion, Samoa, Tonga, Fiji, Micronesia, Mauritius, Guam, and Hawaii (Bedford, 2015).
Adults of this species are best known as pests of the coconut palm (Cocos nucifera). A great many other palms are damaged by adults, including the African oil palm (Elaeis guineensis), betel nut or areca nut palm (Areca catechu), Chinese fan palm (Livistona chinensis), date palm (Phoenix dactylifera), ivory nut palm (Metroxylon amicarum), Fiji fan palm (Pritchardia pacifica), Palmyra palm (Borassus flabellifer), Pandanus spp., ruffle palm (Aiphanes horrida), royal palm (Roystonea regia), sugar palm (Arenga pinnata), and talipot palm (Corypha umbraculifera). Non-palm species recorded as hosts include the Alexandria laurel (Calophyllum inophyllum), banana (Musa spp.), breadfruit (Artocarpus spp.), mango (Mangifera spp.), pineapple (Ananas comosus), and sugarcane (Saccharum spp.) (Molet, 2013).
(Molet, 2013): Females deposit eggs in burrows dug into mulch, decaying vegetation, manure-rich soils, or soft rotten wood. Standing, dead palms are used as breeding sites, as is rotten plant matter caught in the petioles of living palms. Adults burrow as deep as 50 cm (19.7 in) into the crowns of host plants. Adults prepare the burrow for larvae by covering eggs with chewed nesting medium. Females lay three or four clutches of about 30 eggs each. With favorable conditions, there may be up to three overlapping generations per year. The larval stage is 72–130 days, followed by a pre-pupal stage, and then a pupal stage that lasts 31–40 days before adult emergence. Adults are nocturnal.
Severe. Oryctes rhinoceros is a severe and known biosecurity threat with a history of invasive spread. Damage is caused when young adults bore into the crowns of host plants, burrowing as deep as 50 cm into the host tissue (Molet, 2013). This often results in destruction of unopened leaves and damage of the leaf midrib (Molet, 2013). After feeding on the juices produced by damaged host tissue, the beetle bores out of the host, often through the base of the frond (Molet, 2013). Plants, particularly young plants, can be killed when the scarab damages the apical meristem or via secondary infection in the feeding burrow (Hinckley, 1973). In Palau, Gressitt (1953) attributed coconut palm mortality rates of 50% to damage caused by this beetle. Even when coconut palms are not killed in this manner, fruit production is adversely impacted. Estimates of fruit set reduction range from 5 to 25% (Bedford, 2015). Larvae of this species are not reported as pests.
Established. This species is currently established on Oahu where it was first detected in December 2013 on Pearl Harbor-Hickam Joint Base (Hawaii Department of Agriculture, 2014). Efforts are underway to eradicate the scarab and prevent its spread from Oahu. It is very likely that this destructive scarab reached Hawaii by hitchhiking on aircraft flying to Oahu from Guam, a known dispersal pattern for several other invasive scarabs (Moore, 2012).
Established. Oryctes rhinoceros was first recorded in Guam in 2007 in the Tumon Bay area and has spread to the remainder of the island since that time (Moore, 2007). It has been suggested that the current infestation originated from the Phillipines (DeNitto et al., 2015).
This species has been intercepted in quarantine on multiple occasions, with at least five U.S. interceptions known (Molet, 2013). Adults have been recorded on coconut "materials", military equipment and air cargo, and in potted plants (Molet, 2013; Bedford, 2015). It has been reported that larvae are able to survive in floating logs in the ocean (Molet, 2013). The distribution of the species correlates with its primary host, the coconut palm. As such, it should be regarded as a serious potential threat to territories where coconut palms occur: Florida, Puerto Rico, and the U.S. Virgin Islands. Because Oryctes rhinoceros also damages other palms, it should also be regarded as a potential threat to states such as California, Arizona, Texas, Louisiana, Mississippi, Alabama, Georgia, and the Carolinas.
Males of these species can readily be separated by examining the male head horn (Oryctes rhinoceros with a single unbranched horn that ends in single point versus Xylotrupes with a bifurcate horn that ends in two points versus T. dichotomus with a horn that is doubly bifurcate and ends in four points).
Females can be separated by examining the ocular canthus (O. rhinoceros lacks a produced canthus versus Xylotrupes species that have a quadrately produced canthus, T. dichotomus with an acutely produced canthus) and the form of the pronotal depression (O. rhinoceros with broad, sculpted depression versus Xylotrupes without an anterior depression or fovea and T. dichotomus with a distinct fovea).
Oryctes stentor Laporte (Comte de Castelau), Scarabaeus rhinoceros Linnaeus
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Oryctes rhinoceros (coconut rhinoceros beetle) larva in comparison with Protaetia orientalis (Asian flower beetle); photo by M.L. Jameson