Family: Scarabaeidae Subfamily: Melolonthinae Genus: Holotrichia Species: Holotrichia bipunctata Brenske, 1892
Total body length 13.8–18.1 mm (0.54–0.71 in). Body shape cylindrical, somewhat elongate. Color yellowish-brown. Antennae 10-segmented; club 3-segmented; male club slightly shorter than segments 2-7; female club half the length of segments 2-7. Clypeus reflexed; sinuate. Head with weak ridge at base of frons. Pronotum with obvious constriction posterior to apical angle; female with distinct fovea at each side of anterior margin; male lacking fovea. Elytra smooth; lacking prominent setae.
(Boving, 1945): Grub C-shaped, not hump-backed, cylindrical, whitish, numerous dark spots on body. Maxilla with galea and lacinia fused. Mandible with basolateral region with 7 setae; dorsoexterior region lacking setae and punctures. Epipharynx haptomerum with 9 heli. Proplegmatium absent. Last antennal segment with single large, oblong, dorsal sensory spot. Respiratory plates of spiracles cribriform, not constricted. Raster with closely set palidia. Pali short, pointed, slightly curved. Anal opening V-shaped.
Philippines. This species is native to the island of Mindanao, the southernmost of the major Philippine Islands (Cartwright and Gordon, 1971). This beetle is also known from the Philippine island of Luzon (Oakley, 1945).
This species feeds on a variety of cultivated and wild plants. Amongst plants of economic interest, adults have been found on: avocado (Persea spp.), banana (Musa spp.), breadfruit (Artocarpus altilis), cassava (Manihot esculenta), coconut (Cocos nucifera), coffee (Coffea spp.), corn (Zea mays), and kapok (Ceiba pentandra) (Oakley, 1945). Larvae also attack plants, feeding on the roots of beans (Phaseolus spp.), citrus (Citrus spp.), coconut (Cocos nucifera), corn (Zea mays) (Oakley, 1945), and rice (Oryza sativa) (Litsinger et al., 2002).
(Oakley, 1945): Adults of this beetle are generalist herbivores, feeding at night on the foliage of a variety of plant species. At daybreak, adults fly to the ground and burrow into the soil, re-emerging at dusk. In Guam, there appears to be one generation per year with adult activity peaking in March and April. Females deposit eggs 10–15 cm (4–6 in) under loose soils. Larvae emerge from their eggs after 11–15 days. The larval stage lasts 290–309 days and is followed by a 14–15 day pupal stage.
Significant. This species is a pest as both a larva and adult. The larvae are significant pest in upland rice fields in their native range (Litsinger et al., 2002). Larvae are also known to feed on corn roots resulting in major (Oakley, 1945) to minor (Anonymous, 1984) crop loss. Adults damage above-ground plant parts, feeding on the leaves of important crops such as coconut, coffee, and breadfruit (Oakley, 1945). Due to the negative economic potential of this species, it is regarded as a Class B pest by the USDA (USDA APHIS, 2012).
Not established or recorded. There are no records of this species from Hawaii.
Established. This now common species was first detected in 1936 (misidentified as H. mindanaona) by Swezey, with a more ambiguous record that dates to 1931 (Oakley, 1945). It is now established across the island.
This species comes to lights at night and could be attracted to well-lit ports and airports. This would allow for hitchhiking on marine or air cargo. Cartwright and Gordon (1971) suggested that the beetle reached Guam by hitchhiking aboard military aircraft flying between Guam and U.S. bases in the Philippines. As such, Holotrichia bipunctata has a high likelihood of arriving to Hawaii from Guam in the future.
This species is quite similar to the closely related ephilida may beetle (Phyllophaga ephilida). They are differentiated by examination of the head (H. bipunctata with a weak ridge at base of the frons versus P. ephilida which lacks the ridge) and pronotum (H. bipunctata with obvious constriction posterior to apical angle; female with distinct fovea at each side of anterior margin versus P. ephilida without constriction or fovea in either sex).
Phyllophaga bipunctata (Brenske)
In Guamanian literature, there is considerable confusion between this species and the very similar H. mindanaona. Early reports of Ancylonycha (=Holotrichia) from Guam refer to H. mindanaona. This is also the case for Boving's (1945) larval description. However, later checklists make no mention of H. mindanaona, instead referring to H. bipunctata (Cartwright and Gordon, 1971; Bourquin, 2002). To resolve this discrepancy, Guamanian specimens were compared with the type specimens of both H. mindanaona and H. bipunctata (both being valid species). Based on careful examination of type specimens, the Guamanian specimens were identified as H. bipunctata. It is likely then that reports H. mindanaona were misidentifications. It is still possible that both Holotrichia species occur (or occured) on Guam, though all Holotrichia specimens from Guam we examined were identified as H. bipunctata.
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