Hawaiian stag beetle
Only male specimens known (Paulsen and Hawks, 2014). Total body length 16.5–23.0 mm (0.64–0.91 in). Body somewhat oval-shaped, pronotum posterior base constricted; lacking flight wings. Color dull black. Mandibles falcate; lacking internal teeth; surface with small tubercles or granulosites. Ocular canthus indistinct. Front tibia gradually expanded toward a greatly broadened apex; with 1 broad apical tooth and 1 weak external tooth; apical spur peg-like.
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. Both known specimens of this rare beetle were collected near Kaumakani (formerly known as Makaweli) at about 1000 m (3,200 ft).
Probably none. This species is not known to feed on living plant tissues. However, larvae of related Apterocyclus 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. 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. Apterocyclus 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, very rare. Known only from Kauai. Apterocyclus kawaii is known from only two specimens (Paulsen and Hawks, 2014). Like the other native stag beetles, this species presumably has 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 kawaii is one of five Apterocyclus known from Kauai. It can be separated from other native stag beetles by examination of the male mandibles (A. kawaii with mandibles short, falcate; surface with numerous small tubercles or granulosites versus A. palmatus with tusk-like mandibles, all other Apterocyclus with mandible surface lacking small tubercles or granulosites), ocular canthus (A. kawaii with canthus indistinct versus A. honoluluensis with distinct ocular canthus), and front tibia (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 versus A. munroi tibia moderately expanded toward apex; external margin with 2 teeth at apex (appearing somewhat bidentate); with 2–5 small, basal external teeth; apical spur thin and projecting forward, A. honoluluensis tibia moderately expanded toward apex; external margin with a single, apical tooth, variable number of small external teeth; apical spur projecting forward, 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. waterhousei with front tibia enlarged from base; apical tooth small or lacking, numerous small external teeth; apical spur small 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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