Apetasimus 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 : 25-26

Apetasimus Sharp

TYPE SPECIES: Apetasimus involucer Scott in Sharp & Scott, 1908: 458 (monotypy). Brachypeplus: Sharp, 1881: 513 . (syn. in part).

Apetasimus Sharp in Sharp & Scott, 1908: 458. [n. gen., n. sp.].

Orthostolus (in part, species 5–9) Sharp in Sharp & Scott, 1908: 454. (n. syn.). Cyrtostolus Sharp in Sharp & Scott, 1908: 457 (n. syn.)

TYPE SPECIES: Cyrtostolus subalatus Scott in Sharp & Scott, 1908: 457 (monotypy). Apetasimus: Ewing, 2006 [syn., n. spp., key].

Diagnosis: Size small to large, 4.0–8.3 mm L, 1.7–2.9 mm W. Color dark yellow, pale to dark red, pale to dark brown, or black, often with pale yellow to red areas on elytra, rarely head, prothorax, or abdomen dark brick red. Perisac with dorsal sclerites-primary appressed to the flagellum proximally. Flagellum short, directed ventroproximally. Perisac dorsoventrally attenuate distally (fig. 12). Dorsal incision deep, 3/4 of perisac length, ventral incision shallower, 1/5 of length or less. Microsculpture of dorsum usually granulate, rarely subobsolete and glabrous.

Description: Eyes small with 18–21 facets to reduced with 6–12 facets (specimens with reduced eyes also with tarsal lobes and wings reduced, and margin of elytron widely explanate), never reaching margin of postgena; temple wide; postgena straight, convex, or weakly concave; angle formed with occiput oblique. Antennal grooves weakly convergent, medial margin usually nearly obsolete, rarely definite, lateral margin less distinct; antennal club compact, 9th antennomere transverse. Labrum broad and deeply to narrow and shallowly emarginated, with a short, acute projection medially, brushes of short setae present laterad of projection, longer setae present near lateral angle. Mandible with apex simple or bicuspid, subapical teeth 2–5. Third labial palpomere diverse: quadrate, sub quadrate and nearly parallel sided, subquadrate and wider at base, or elongate and spindle shaped. Paraglossae small, moderately projecting laterad and broadly rounded at apex.

Pronotum variable, always transverse and narrowed anteriorly; usually moderately convex, rarely depressed; widest near middle, rarely posterad of middle; hind angle usually sinuate, rarely obtusely rounded; anterior margin shallowly to deeply emarginate; hind margin bisinuate. Prosternal process diverse, small and upturned to broad and little upturned posterad of procoxae.

Elytron 2x as long as wide or less; lateral margin narrow to widely explanate; punctures of elytron definite, striae often irregular, interstices little raised, often with thickenings bearing tufts of setae, thickenings sometimes paler. Elytra usually exposing abdominal segments 7, 6, and part of 5.

Tarsomeres 1–3 variable, from strongly dilated to lobes obsolete.

Metacoxal process of 3rd abdominal segment wide. Male pygidium broadly rounded to subtruncate, rarely subtruncate and shallowly and broadly emarginate with lateral margins sometimes forming small teeth; terminal ventral strongly to weakly bisinuate. Anal sclerite from parallel sided to strongly convergent apically, apex shallowly emarginate, truncate, or acute. Female pygidium broadly rounded, subtruncate, to very weakly and narrowly emarginate; terminal ventral subtruncate, broadly rounded, rarely weakly bisinuate. Gonocoxites elongate. Basal ring of spermatheca strongly sclerotized.

Apetasimus was based on Apetasimus involucer Scott , a species of small body size (~ 4 mm) characterized by reduced flight wings. Recent collections and subsequent analyses have identified three distinct lineages ( Ewing 2006). There are three species, recently collected on Oahu, Molokai, and East Maui, that are closely related to A. involucer . Two new fully winged species, one from Kauai and one from Hawaii Island, form a second lineage. The third lineage comprises six species, all apparently associated with Acacia koa . These were formerly placed in Orthostolus , and have not been collected since the 1930's. Similarities between A. involucer and the six species formerly placed in Orthostolus and Cyrtostolus was noted in the description of the genus Apetasimus ( Sharp & Scott 1908) . Details of the form of the male internal copulatory sac support the transfer of these six species from Orthostolus to Apetasimus ( Ewing 2006) .

The six species formerly placed in Cyrtostolus and Orthostolus are apparently all extinct, with the last collections made in the 1930's. All of these species were exclusively or primarily collected subcortically on Acacia koa ( Blackburn & Sharp 1885; Perkins 1892–1897; Sharp 1881; Sharp & Scott 1908). Carabid beetles associated with the same micro-habitat apparently went extinct around the same time on Maui ( Liebherr 2004). These extinctions are correlated with the spread of adventive isopods ( Taiti & Howarth 1996) which disrupted the subcortical Koa micro-habitat, possibly displacing the fungi on which the sap beetles depended. There is no host data for the type of the genus, A. involucer , though close relatives on Molokai and Maui were collected by fogging moss mats on Metrosideros and Cibotium trunks respectively ( Ewing 2006). The most common species, A. pleomelarrosus Ewing , is found within the leaf axils of Pleomele trees in the Kokee area of Kauai. It is most plentiful in trees that have been stressed by breakage or blow down. They feed by chewing grooves in the leaf bases and presumably feed on fungi growing within the resulting sap flow ( Ewing 2006).