Hawaiian stag beetle
Family: Lucanidae Subfamily: Lucaninae Genus: Apterocyclus Species: Apterocyclus waterhousei Sharp, 1908
Total body length 18.0–22.0 mm (0.71–0.87 in). Body elongate-oval, thorax constricted anterior to elytra; flight wings lacking. Color dull black. Mandibles falcate; with single internal tooth; surface lacking small tubercles or granulosites. Ocular canthus indistinct. Front tibia expanded from base; apical tooth small or lacking, numerous small external teeth; apical spur small and projecting forward.
Undescribed. For Lucaninae (Ritcher, 1966): Grub C-shaped, not hump-backed, cylindrical, whitish. Mandible with a ventral process; left molar with inner margin distad of the molar areas with one or more teeth. Maxillary stridulatory teeth usually absent. Maxillary palpus 4-segmented. Thoracic spiracles with emarginations of respiratory plates facing anteriorly. Legs not reduced in size; stridulatory organs present on front and middle legs. Middle leg with trochanter with a stridulatory area consisting of a single longitudinal row of very short transverse ridges. Raster with 2 patches of spine-like setae.
Kauai. Specimens have been collected from a small number of sites in northwestern Kauai including Kohua Stream, Kaholuamano, Waialae River, Po'omau Canyon, and Kohua Ridge (Paulsen and Hawks, 2014).
Probably none. This species is not known to feed on living plant tissues. However, adults and larvae are known to be closely associated with dead logs of the native Hawaiian koa tree (Acacia koa) (Osborn, 1920; Paulsen and Hawks, 2014).
Poorly known. Related Apterocyclus species are associated with native Hawaiian koa (Acacia koa) forests at high elevations. Here, flightless adults and larvae burrow amongst rotting koa logs (Van Dyke, 1922), with larvae presumably feeding upon the decaying wood and perhaps associated fungus.
None. Apterocylus species are not known to feed on living plants. This, combined with their great rarity and dependence on undisturbed native habitat, greatly limits any pest potential.
Native and rare. Known only from Kauai. Like the other native stag beetles, this rare species has presumably suffered from a combination of habitat loss and heavy predation from non-native rodent species (Howden, 2008).
Not established or recorded. There are no records of this species from Guam.
All Apterocyclus species are flightless, rare, and dependent upon vanishing native Hawaiian habitat. As such, members of this genus are unlikely to spread beyond their small natural ranges.
Apterocyclus waterhousei is one of five Apterocyclus known from Kauai. It can be separated from other native stage beetles by examination of the male mandibles (A. waterhousei male with mandibles falcate; with single internal tooth; surface lacking small tubercles or granulosites versus A. palmatus male with tusk-like mandibles, A. kawaii male without internal tooth; surface with many small tubercles or granulosites), ocular canthus (A. waterhousei with ocular canthus indistinct versus A. honoluluensis with distinct ocular canthus), and front tibia (A. waterhousei with front tibia expanded from base; apical tooth small or lacking, numerous small external teeth; apical spur small and projecting forward versus A. palmatus with front tibia expanded toward apex with apical ¼ greatly produced; with 1 large apical tooth and 1 large external tooth; apical spur enlarged and projecting medially, A. kawaii with front tibia gradually expanded toward a greatly broadened apex; with 1 broad apical tooth and 1 weak external tooth; apical spur peg-like, A. honoluluensis with front tibia moderately expanded toward apex; external margin with a single, apical tooth, variable number of small external teeth; apical spur projecting forward, A. munroi tibia moderately expanded toward apex; external margin with 2 teeth at apex (appearing somewhat bidentate); with 2-5 small external teeth; apical spur thin and projecting forward).
Images temporarily unavailable, see:
Paulsen M, Hawks D. 2014. A review of the primary types of the Hawaiian stag beetle genus Apterocyclus Waterhouse (Coleoptera, Lucanidae, Lucaninae), with the description of a new species. ZooKeys 433: 77–88. doi: 10.3897/zookeys.433.8022
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