Apterocyclus palmatus

Status

Extirpated

Common name(s)

Hawaiian stag beetle

Taxonomy

Family: Lucanidae Subfamily: Lucaninae Genus: Apterocyclus Species: Apterocyclus palmatus Van Dyke, 1921

DNA barcode

none available

Adult diagnosis

Only male specimens known (Paulsen and Hawks, 2014Paulsen and Hawks, 2014:
Paulsen M and 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). Total body length 22.0–23.0 mm (0.86–0.90 in). Body elongate-oval, thorax constricted anterioranterior:
the front or forward; opposite of posterior
to elytra; flight wings lacking. Color dull black. MandiblesMandibles:
The crushing or chewing portion of an insects mouthparts
elongate, tusk-like; lacking internal teeth; surface lacking small tubercles or granulositesgranulosites:
relating to a coarse, grainy surface texture
. Ocular canthuscanthus:
a process extending over and sometimes dividing the eye
indistinct. Front tibiatibia:
a segment of the leg articulated with the tarsus and femur
greatly expanded at apexapex:
point or edge furthest from the body
with 1 large apical toothtooth:
a pointed process from an appendage or margin, often in reference to the tibia
and 1 large external toothtooth:
a pointed process from an appendage or margin, often in reference to the tibia
; apical spurspur:
movable, spine-like process, sometimes mobile, often found at or near the tibial apices
enlarged and projecting medially.

Larval diagnosis

Undescribed. For Lucaninae (Ritcher, 1966Ritcher, 1966:
Ritcher P. 1966. White grubs and their allies: a study of North American scarabaeoid larvae. Oregon State University Monographs, Studies in Entomology 4: 1-219.): Grub C-shaped, not hump-backed, cylindrical, whitish. Mandiblemandible:
The crushing or chewing portion of an insects mouthparts
with a ventralventral:
of or relating to the lower surface; opposite of dorsal
process; left molar with inner margin distaddistad:
oriented away from the body or the point of articulation with body
of the molar areas with one or more teeth. Maxillary stridulatory teeth usually absent. Maxillary palpusmaxillary palpus:
multi-segmented sensory organ/appendage of the maxilla
4-segmented. Thoracic spiraclesspiracles:
opening on the abdomen or thorax through which air enters and exits the body
with emarginations of respiratory plates facing anteriorly. Legs not reduced in size; stridulatory organs present on front and middle legs. Middle leg with trochantertrochanter:
a segment of the leg articulated with the femur and coxa
with a stridulatory area consisting of a single longitudinal row of very short transversetransverse:
extending horizontally across a surface
ridges. Rasterraster:
in scarab larvae, a complex of setose, spiny, and bare areas on the ventral surface of the last abdominal segment
with 2 patches of spine-like setaesetae:
small, hair-like structure
.

Native range

Kauai. Distribution data for this species is particularly scarce. The limited information available from museum specimens indicates that it occurs only on Kauai above elevations of 1,200 m (4,000 ft) (Paulsen and Hawks, 2014Paulsen and Hawks, 2014:
Paulsen M and 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).

Plant host(s)

Probably none. This species is not known to feed on living plant tissues. However, larvaelarvae:
the immature form of an insect; in scarabs, also called grub or white grub; preceded by the egg stage, followed by the pupal stage
of related Apterocyclus are known to be closely associated with dead logs of the native Hawaiian koa tree (Acacia koa) (Osborn, 1920Osborn, 1920:
Osborn, HT. 1920. A note on Apterocyclus (Coleoptera, Lucanidae). Proceedings of the Hawaiian Entomological Society 4: 375-376. full text (accessed 2015); Paulsen and Hawks, 2014Paulsen and Hawks, 2014:
Paulsen M and 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).

Life history

Poorly known. Related Apterocyclus species are associated with native Hawaiian koa (Acacia koa) forests at high elevations. Here, adults and larvaelarvae:
the immature form of an insect; in scarabs, also called grub or white grub; preceded by the egg stage, followed by the pupal stage
burrow amongst rotting koa logs (Van Dyke, 1922Van Dyke, 1922:
Van Dyke E. 1922. A study of the lucanid Coleoptera of the Hawaiian Islands. Proceedings of the Hawaiian Entomological Society 5: 39–49. full text (accessed 2015)), and larvaelarvae:
the immature form of an insect; in scarabs, also called grub or white grub; preceded by the egg stage, followed by the pupal stage
presumably feed upon decaying wood and perhaps fungus associated with koa logs.

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. This species has not been collected or recorded in the last 50 years (Paulsen and Hawks, 2014Paulsen and Hawks, 2014:
Paulsen M and 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). Like other native Apterocylcus stag beetles, this species has likely suffered from a combination of habitat loss and heavy predation from non-native rodent species (Howden, 2008Howden, 2008:
Howden H. 2008. In past years - XIII 1970–1974. Scarabs Newsletter 30: 15–21.).

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 palmatus is one of five Apterocyclus known from Kauai. It is separated from other native stag beetles by examination of the male mandiblesmandibles:
The crushing or chewing portion of an insects mouthparts
(A. palmatus male with tusk-like mandiblesmandibles:
The crushing or chewing portion of an insects mouthparts
versus mandiblesmandibles:
The crushing or chewing portion of an insects mouthparts
short and falcatefalcate:
curved, sickle-like
in all other Apterocyclus species), ocular canthuscanthus:
a process extending over and sometimes dividing the eye
(A. palmatus with ocular canthuscanthus:
a process extending over and sometimes dividing the eye
indistinct versus A. honoluluensis with distinct ocular canthuscanthus:
a process extending over and sometimes dividing the eye
), and front tibiatibia:
a segment of the leg articulated with the tarsus and femur
(A. palmatus with front tibiatibia:
a segment of the leg articulated with the tarsus and femur
expanded toward apexapex:
point or edge furthest from the body
with apical ¼ greatly produced; with 1 large apical toothtooth:
a pointed process from an appendage or margin, often in reference to the tibia
and 1 large external toothtooth:
a pointed process from an appendage or margin, often in reference to the tibia
; apical spurspur:
movable, spine-like process, sometimes mobile, often found at or near the tibial apices
enlarged and projecting medially versus A. kawaiiwith front tibiatibia:
a segment of the leg articulated with the tarsus and femur
gradually expanded toward a greatly broadened apexapex:
point or edge furthest from the body
; with 1 broad apical toothtooth:
a pointed process from an appendage or margin, often in reference to the tibia
and 1 weak external toothtooth:
a pointed process from an appendage or margin, often in reference to the tibia
; apical spurspur:
movable, spine-like process, sometimes mobile, often found at or near the tibial apices
peg-like, A. honoluluensis with front tibiatibia:
a segment of the leg articulated with the tarsus and femur
moderately expanded toward apexapex:
point or edge furthest from the body
; external margin with a single, apical toothtooth:
a pointed process from an appendage or margin, often in reference to the tibia
, variable number of small external teeth; apical spurspur:
movable, spine-like process, sometimes mobile, often found at or near the tibial apices
projecting forward, A. munroitibia tibia:
a segment of the leg articulated with the tarsus and femur
moderately expanded toward apexapex:
point or edge furthest from the body
; external margin with 2 teeth at apexapex:
point or edge furthest from the body
(appearing somewhat bidentatebidentate:
a surface that is sharply notched, usually resulting in two tooth-like protrusions on each side of the notch
); with 2-5 small external teeth; apical spurspur:
movable, spine-like process, sometimes mobile, often found at or near the tibial apices
thin and projecting forward, A. waterhouseiwith front tibiatibia:
a segment of the leg articulated with the tarsus and femur
expanded from base; apical toothtooth:
a pointed process from an appendage or margin, often in reference to the tibia
small or lacking, numerous small external teeth; apical spurspur:
movable, spine-like process, sometimes mobile, often found at or near the tibial apices
small and projecting forward).

Other names (synonyms)

Apterocyclus honoluluensis var. palmatus Van Dyke

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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