Gonioryctus Sharp

Ewing, Curtis, 2007, Phylogenetic analysis of the genera of endemic Hawaiian sap beetles (Coleoptera: Nitidulidae) based on morphology with redescription and key to the genera of endemic Hawaiian Nitidulidae, Zootaxa 1427, pp. 1-36 : 20-22

Gonioryctus Sharp

TYPE SPECIES: Gonioryctus latus Sharp, 1878: 129 . (hereby desig.)

Gonioryctus Sharp, 1878: 128 [n. gen.].

Gonioryctus: Sharp in Sharp & Scott, 1908: 440 [redescript., n. spp.].

Goniothorax Sharp in Sharp & Scott, 1908: 436 (junior objective homonym, preoccupied by Goniothorax Milne- Edwards, 1879 [Crustacea],) [n. gen., n. spp.].

TYPE SPECIES: Goniothorax conicicollis Sharp in Sharp & Scott, 1908: 436 (orig. desig.).

Nesapterus Sharp in Sharp & Scott, 1908: 450 (n. syn.) [n. gen. n. sp.].

TYPE SPECIES: Gonioryctus monticola Sharp, 1878: 130 (subs. desig. Sharp in Sharp & Scott, 1908: 450).

Eunitidula Sharp in Sharp & Scott, 1908: 451 [n. gen., n. sp.].

TYPE SPECIES: Eunitidula sublaevis Sharp in Sharp & Scott, 1908: 452 (monotypy).

Diagnosis: Size usually medium to large, 4.0–9.5 mm L, 2.0 –3.5 mm W. Small specimens with wings reduced and margin of elytron explanate. Eyes large, nearly always truncate at postgenae and temple narrow. Antennal club elongate, 9th antennomere subquadrate, surface of club with spiculate microsculpture and setae fine and short. Color yellow to dark brown, pale to dark brick red, to black, sometimes variegate. Microsculpture variable, often granulate, sometimes obsolete and glabrous.

Description: Eyes usually large, facets coarse; temple usually acute and straight to occiput, rarely less acute and very broadly concave; antennal grooves strongly convergent, medial margin well defined and partially covered basally by flange of postgena; antennae robust, club elongate and densely covered with distinct elongate spicules; labrum with medial tooth subacute, subtruncate, rarely obsolete, broadly and shallowly emarginated directly laterad of tooth, gently sloped to curved lateral margin, 2 pairs dorsal macrosetae, medial and lateral ventral apical setal combs continuous and of similar length; mandible robust, apex simple or bicuspid, subapical teeth 3–4, sometimes obsolete; third labial palpomere elongate, apex slightly narrower to distinctly wider than base, paraglossae large, membranous, projected laterally.

Prothorax variable, most commonly transverse (fig. 54), sometimes angular (fig. 51), trapezoidal (fig. 52), elongate and nearly parallel (fig. 53), or sinuate and narrowed behind (fig. 38); lateral margins curved, recurved, angular, or nearly straight; prosternal process posterad of coxae abruptly and little expanded and recurved dorsad, rarely narrow between coxae, evenly and greatly expanded posterad of coxae, when expanded then only moderately reflexed dorsad and dorsal surface of pronotum and elytra glabrous with punctures fine and sparse.

Elytron moderately elongate, each 2x as long as wide or less; lateral margin less than 2x width of marginal bead. Punctures of elytra coarse to very fine, usually forming distinct striae, striae 1–7 usually somewhat irregular, often consisting of 2 confused rows of punctures, striae 8, 9, and 10 irregular. Interstices distinctly raised to obsolete; interstices 3, 5, and 7 often with expansions, not bearing distinct setal tufts. Elytra usually exposing abdominal segments 7, 6, and part of 5.

Tarsomeres 1–3 with ventral lobes progressively dilated and bilobed. Metacoxal process of 3rd abdominal sternite wide. Male pygidium shallowly emarginate, truncate, broadly rounded, or subacute. Anal sclerite bilobed, subtruncate to broadly rounded. Perisac diverse, elongate to short, sclerites well developed to obsolete, uncommonly fused and asymmetrical. Female pygidium broadly rounded to subacute. Gonocoxae elongate, narrow to abbreviated. Basal ring of spermatheca strongly sclerotized.

There are 34 described and at least 13 undescribed species of Gonioryctus . They are primarily associated with woody plants in mesic and wet forests. The genera Goniothorax , Nesapterus , and Eunitidula were proposed for distinctive lineages of Gonioryctus . The close affinity of Goniothorax , Nesapterus , and Eunitidula with Gonioryctus was noted in the respective generic descriptions ( Sharp & Scott 1908), with Goniothorax proposed based on the form of the prothorax and legs, Nesapterus on the form of the wings, and Eunitidula on the form of the prosternal process. Goniothorax is invalid, being previously assigned to a genus of crustacean in 1879 and later to an Australian subgenus of ants in the genus Leptothorax in 1896, with the latter usage the most widely published. Goniothorax , Nesapterus , and Eunitidula are herein synonymized with Gonioryctus . Sharp considered Gonioryctus species to be the "perfect insects" because he believed that the adults were generally very short lived ( Sharp & Scott 1908). The largest individuals of endemic Hawaiian Nitidulidae are in this genus, with some being over 10 mm in length. Individuals of many species perform crepuscular nuptial flights but are very rarely seen flying during the day. Two lineages with reduced flight wings are associated with ferns; one with Cibotium tree ferns (species placed in Nesapterus found on Oahu and Maui Nui), the other with Dryopteris ferns (one species each from Molokai and West Maui, both undescribed).

Gonioryctus species are ecologically diverse; being associated with flowers, detritus in leaf axils, vegetation, and woody plant material. There are two species found on Kauai, with all other species on the younger islands apparently descended from them (Ewing 2005). Gonioryctus anticatus Sharp is a relatively small species that is most commonly collected by beating low ferns such as, Dryopteris , and Diplazium . Gonioryctus kauaiensis is a larger species collected by beating Cheirodendron trunks in a state of decay and at lights. Many of the species related to G. kauaiensis retain an association with trees in the family Araliaceae , especially Cheirodendron . All of the Eunitidula species and the majority of the Goniothorax species are members of the Araliaceae loving lineage. The remaining species previously considered Goniothorax are associated with ferns. Most species of Gonioryctus are known from small series, with many being known from a single specimen or mating pair. They are the most often collected species of endemic Hawaiian Nitidulidae at lights. Specimens have been collected under bark and in wood of decaying trees, in fresh flowers, within dry, decaying lobelioid stems, in decaying Cibotium fern rachi, in leaf axils of Freycinetia and Astelia , and by beating diverse vegetation.

The recognition of Goniothorax as invalid and placement of the species in Gonioryctus requires the following taxonomic changes:

Gonioryctus conicicollis (Sharp) , n. comb.

Goniothorax conicicollis Sharp in Sharp & Scott, 1908: 436. Gonioryctus cuneatus (Sharp) , n. comb.

Goniothorax cuneatus Sharp in Sharp & Scott, 1908: 437. Gonioryctus elongatus (Sharp) , n. comb.

Goniothorax elongatus Sharp in Sharp & Scott, 1908: 437. Gonioryctus plebius (Sharp) , n. comb.

Goniothorax plebius Sharp in Sharp & Scott, 1908: 437. Gonioryctus perkinsi (Sharp) , n. comb.

Goniothorax perkinsi Sharp in Sharp & Scott, 1908: 438. Gonioryctus fugitivus Blackburn

Gonioryctus fugitivus Blackburn in Blackburn & Sharp, 1885: 131. Goniothorax fugitivus: (Blackburn) (Sharp) in Sharp & Scott, 1908: 438. Gonioryctus inaequalis (Sharp) , n. comb.

Goniothorax inaequalis Sharp in Sharp & Scott, 1908: 438. Gonioryctus eremitus (Sharp) , n. comb.

Goniothorax eremitus Sharp in Sharp & Scott, 1908: 439. Gonioryctus foveatus (Sharp) , n. comb.

Goniothorax foveatus Sharp in Sharp & Scott, 1908: 439.

The placement of Nesapterus and Eunitidula as junior synonyms under Gonioryctus requires the following taxonomic changes:

Gonioryctus monticola Sharp

Gonioryctus monticola Sharp, 1878: 130 .

Nesapterus monticola: (Sharp) in Sharp & Scott, 1908: 451.

Gonioryctus exilis (Sharp) , n. comb.

Nesapterus exilis Sharp in Sharp & Scott, 1908 451. Gonioryctus sublaevis (Sharp) , n. comb.

Eunitidula sublaevis Sharp in Sharp & Scott, 1908: 452.