Akalyptoischion Andrews 1976

Hartley, Christopher S., Andrews, Fred G. & Mchugh, Joseph V., 2007, A Taxonomic Revision Of The Genus Akalyptoischion Andrews (Coleoptera: Latridiidae), The Coleopterists Bulletin (mo 6) 61, pp. 1-50 : 6-10

Akalyptoischion Andrews 1976

Type Species: Akalyptoischion tomeus Andrews 1976 a:11 .

Diagnosis. Akalyptoischion is distinct from all other Latridiidae in having posteriorly open procoxal cavities ( Fig. 2). Other diagnostic characters are the large, protruding, laterally expanded labrum ( Figs. 1, 30–35), small eyes situated at the posterior corners of the head ( Figs. 1, 30–35), large, well-sclerotized mandibles ( Figs. 6, 7, 37, 40), and pseudosegmented first tarsomeres ( Figs. 19–21, 27).

Description. Length 0.95–1.80 mm; width 0.22–0.62 mm. Body shape elongate; dorsoventrally compressed with somewhat convex elytra ( Fig. 1). Subglabrous to densely setose. Color uniformly light brown or reddish brown to nearly black, occasionally with head and prothorax darker than elytra.

Head prognathous, trapezoidal, narrowing anteriorly, widest posteriorly with an acute constriction posterior to eyes; frontoclypeal suture distinct. Dorsal surface densely and irregularly punctate, punctures coarse or fine. Usually with a pair of distinct dorsal foveae at midline. Clypeus ( Figs. 1, 30–35) narrowing sharply anterior to antennal insertions, truncate anteriorly, with a large crescent-shaped fovea posteriorly. Eyes ( Figs. 1, 30–35) small, composed of 2–6 large or small facets, situated at posterior corners of head. Antennae ( Fig. 3) 11-segmented; antennomere I large, irregularly shaped, subglobular; II subglobular or elongate oval; III–VIII elongate, parallel sided or as long as wide, submoniliform; IX–XI or X–XI enlarged to form a densely pubescent, sensilla-bearing club ( Fig. 29); IX globular or elongate and widening apically, conical; X about as wide as long; XI wider than long, subrectangular or trapezoidal. Labrum large, projecting anteriorly, laterally expanded, wider than clypeus; densely setose, setae often twice length of labrum; lateral margins arcuate to nearly parallel sided, anterior margin slightly emarginate ( Fig. 8) to deeply emarginate ( Fig. 9). Mandible ( Figs. 6, 7) with narrow, pointed apex with an apical tooth and 1–5 subapical teeth ( Fig. 6) or broad apex with large apical tooth and 1–3 bicuspid subapical denticles ( Fig. 7); prostheca membranous with a fringe of long setae that are bifid subapically. Maxilla ( Fig. 5) with lacinia distinct but highly reduced, bearing several long setae in a medial longitudinal row and at apex, galea broad, with setose apex; maxillary palp 4-segmented; palpomere I elongate, slender, curved, II large, asymmetrically inflated and round, III large and oval, IV elongate, subrectangular or acuminate. Ventral surface of head usually punctate, with a large transverse fovea usually apparent on the submentum immediately adjacent to its articulation with the mentum ( Figs. 25, 36–41). Mentum ( Fig. 4) trapezoidal with various foveae; ligula small, undivided; labial palp 1- segmented, palpomere large, narrowing apically with apical setose area.

Pronotum convex, median portion elevated, lateral edges explanate, sometimes greatly so; densely and irregularly punctate on elevated medial part; with 2 pairs of foveae, one anterior and one posterior, present on lateral edges and base of raised area ( Figs. 42–47); anterior and posterior margins evenly arcuate, lateral margins arcuate to straight sided, with tubercles usually bearing setae; anterior angles gently rounded ( Figs. 42, 45–47), right angled ( Figs. 12, 43, 44), or slightly lobed ( Fig. 13); prosternum with a lateral line of punctures anteriorly and with scattered punctures posteriorly, prosternal process narrow, keeled and elevated above coxae; procoxal cavities widely open posteriorly ( Fig. 2).

Pterothorax narrow anteriorly, gradually broadening posteriorly; mesosternum with sinuate anterior edge, usually punctate, sometimes with carinae, division between sternum and pleura distinct posteriorly, becoming less distinct anteriorly ( Fig. 22), mesosternal process keeled and elevated; metasternum visibly convex, inflated, usually with a deep fovea between mesocoxae, a deep fovea posterior to each mesocoxa, an oval to arcuate fovea anterior to each metacoxa, and a long transverse fovea between metacoxae for reception of abdominal intercoxal process; median surface of metasternum may be irregularly punctate ( Fig. 23–24) or without punctures ( Fig. 48). Procoxa appearing round with concealed lateral expansions ( Figs. 2, 21), mesocoxa ( Fig. 20) and metacoxa rounded ( Fig 19); trochanters heteromerous, femur reaching coxa; femur sparsely setose, prothoracic femur deeply grooved ventrally to receive tibia ( Fig. 21), meso and metathoracic femora less deeply grooved ( Figs. 19, 20); tibia narrowest and slightly curved basally, sparsely setose with a U-shaped ring of short, stout setae at apex ( Figs. 19– 21); tarsi intermediate between 3-3-3 and 4-4-4, tarsomere I apparently a composite of 2 fused segments with pseudosegmentation indicated by an annulation and by the pattern of setation ( Fig. 27); tarsomeres otherwise simple, apical tarsomere as long as others combined, basal 2 tarsomeres with paired stout setae ventrally, apical tarsomere moderately clothed with simple setae, tarsal claws simple. Scutellum very small, triangular, hidden beneath elytra. Elytra wider than prothorax, covering entire abdomen, flattened dorsally, evenly rounded posteriorly, sometimes with a lateral flange; elytral suture connate; dorsal surface usually with 6 rows of large, single punctures, a seventh row rarely present; strial interspaces usually bear erect or decumbent setae, strial interspaces 1, 3, and 5 may be flat, gently convex or sharply carinate; metathoracic wings lacking.

Abdomen with 5 ventrites, ventrite I twice length of remaining ventrites, with a large fovea posterior to each metathoracic coxa and usually bifoveolate on intercoxal process ( Figs. 11, 17), medial surface with punctures ( Figs. 11, 17, 50) or unmarked ( Figs. 10, 49, 51–53); ventrites II–V with a deep basal depression extending nearly across ventrite ( Figs. 17, 28); male genitalia a simple curved tube, accessory appendages lost.

Distribution. Akalyptoischion is limited to western North America, though its exact limits remain unclear. It is currently known from California to western Texas and from Baja California Sur to southern Oregon and Idaho. The new data reported here represent a significant range expansion for the genus over that originally reported by Andrews (1976 a). More extensive Berlese sampling in the western United States and Mexico may further increase the known range of the genus.

Remarks. This genus superficially resembles Dienerella , Metophthalmus , and Adistemia in that they have small eyes composed of few facets and distinct elytral striae with large strial punctures. Akalyptoischion is easily distinguished from these genera and from all other Latridiidae by its open procoxal cavities and its pseudosegmented basal tarsomere.