Apterocyclus munroi


Common name(s)

Hawaiian stag beetle


Family: Lucanidae Subfamily: Lucaninae Genus: Apterocyclus Species: Apterocyclus munroi Sharp, 1908

Adult diagnosis

Only male specimens known (Paulsen and Hawks, 2014). Total body length 18.0 mm (0.71 in). Body somewhat oval-shaped, pronotum posterior base constricted; lacking flight wings. Color dull black. Mandibles falcate; with single internal tooth; surface lacking small tubercles or granulosites. Ocular canthus indistinct. Front tibia moderately expanded toward apex; external margin with 2 teeth at apex (appearing somewhat bidentate); with 2-5 small, external basal teeth (smaller than apical teeth); apical spur thin and projecting forward.

Larval diagnosis

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.

Native range

Kauai. Type specimens were collected at about 600–900 m (2,000–3,000 ft) on Kauai, one was recorded near Kaumakani (formerly Makaweli) (Paulsen and Hawks, 2014).

Plant host(s)

Probably none. This species is not known to feed on living plant tissues. However, adults and larvae of related species are known to be closely associated with dead logs of the native Hawaiian koa tree (Acacia koa) (Osborn, 1920; Paulsen and Hawks, 2014).

Life history

Poorly known. Related Apterocyclus species are associated with native Hawaiian koa (Acacia koa) forests at high elevations. Here, adults and larvae burrow amongst rotting koa logs (Van Dyke, 1922), and larvae presumably feed upon the decaying wood and perhaps associated fungus.

Pest potential

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.

Status in Hawaii

Native (possibly extinct). Known only from Kauai. Apterocyclus munroi is known from only four specimens, and it has not been collected since 1908 (Paulsen and Hawks, 2014). Like the other native stag beetles, this species has presumably suffered from a combination of habitat loss and heavy predation from non-native rodent species (Howden, 2008).

Status in Guam

Not established or recorded. There are no records of this species from Guam.

Potential distribution and dispersal pathway

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.

Similar species

Apterocyclus munroi is one of five Apterocyclus known from Kauai. It is separated from other native stage beetles by examination of the male mandibles (A. munroi with short, falcate mandibles; surface lacking small tubercles or granulosites versus A. palmatus with tusk-like mandibles, A. kawaii with mandibles short, falcate; surface with numerous small tubercles or granulosites), ocular canthus (A. munroi with canthus indistinct versus A. honoluluensis with distinct ocular canthus), and front tibia (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 versus 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. 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. waterhousei with front tibia enlarged from base; apical tooth small or lacking, numerous small external teeth; apical spur small and projecting forward).

Other names (synonyms)

Apterocyclus adpropinquans Sharp

Special note

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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Acacia koa in bloom; photo by M.L. Jameson

Acacia koa in bloom; photo by M.L. Jameson

distribution map for Apterocyclus munroi

distribution map for Apterocyclus munroi