Ogdoecosta Spaeth 1909

Ogdoecosta Spaeth 1909: 718

Ogdoecosta juvenca (Boheman 1854) Type species designated by Hincks (1952).

Redescription. Adult body shape oval; body length varies from 7.7–11.6 mm in males (n=38) and 10–13 mm in females (n=42); elytra with diverse color patterns.

HEAD. Head cylindrical, retracted into pronotum, visibility partial from above. Vertex between eyes coarsely punctate, bordered by a cariniform elevation; surface sparsely pubescent; median sulcus present (Fig. 2 A), extending from anterior margin of frontoclypeus, between eyes, to slightly beyond posterior eye margin; surface bordering median sulcus with small carina. Eyes prominent, finely faceted, occupying ¾ length of lateral margin of head, separated by antennal insertions. Antennae filiform (Fig. 2 B), with 11 antennomeres, without variation in form or color between species; scape, pedicel and antennomeres III–V shiny amber colored and sparsely setose; basal antennomeres internally infuscate and amber colored; setae long, scattered. Antennomere I can be shorter or longer than antennomere XI; antennomere III can be shorter or longer than antennomere IV; antennomere II always shorter than I and III; antennomeres VI–IX almost square-shaped, with short dense setae; antennomeres V–XI widening apically (Fig. 2 B); antennomere XI oval-shaped. Gena surface varies from smooth to rugose, sparsely pubescent. Clypeus protuberant, margins obvious, shape subtrapezoidal or oval (Figs 2 C, D); surface coarsely punctate, pubescent. Labrum prominent, surface smooth with long setae; apical margin emarginated (Fig. 2 E). Mandible palmate, well sclerotized; middle-part of external surface projected, with some setae; distal margin with five teeth in all species; three basal teeth with apex triangular in shape; two apical teeth with apex rounded (Fig. 2 F). Labium with mentum long as wide, with medial groove; ligula with rounded apical margin and long, sparse setae; labial palps with three palpomeres, some with setae; palpomere III finely acute (Fig. 3 A). Maxilla with membranous lacinia, apex round; maxillary palps with three palpomeres; palpomere II setose at apex; palpomere III rounded at apex, setose on lateral margins (Fig. 3 B).

THORAX. Pronotum transverse, frequently more than twice as wide as long; surface sparsely punctate, punctures fine (e.g., O. epilachnoides) to rugose. Anterior margin broadly emarginated, margination U or Vshaped; posterior margin projected medially, truncate at scutellum; antero-lateral angles slightly projected posterolaterad. Disc with median groove oriented longitudinally; groove incomplete posteriorly, in some species very faint or absent. Prosternum smooth, wrinkled at lateral? margins; prosternal collar rugose, constrained medially, expanded over mouth up to mandible. Scutellum always triangular, black; anterior margin concave, covered by pronotal margin. Elytra generally semi-circular (males in some species circular); surface pubescent or glabrous, variable pattern of spots; anterior margin serrate; humeri obliquely truncate; epipleura clearly sinuous in O.

biannularis, O. fasciata and O. mexicana (Fig. 3 C). Prosternal process with central impression; apex dilated, with long expanded setae in some species; mesosternum concave, hind apex emarginated; metasternum transverse. Procoxa and mesocoxa conical; metacoxa tranverse; trochanter triangular; femur fusiform; tibia pubescence scattered, apex broad with longer setae, dorsal surface canaliculate. Tarsomeres II and III bilobed; tarsomere I shorter than others; tarsomere III and V generally similarly sized; tarsomere I–III with long setae; tarsomere V with fewer setae; claws appendiculate.

ABDOMEN. Surface smooth, glabrous or pubescent, shiny. Pygidium with pubescence dense at apex. Both sexes in all species have sternite V with lateral impressions; impressions less visible in some species. Male genitalia: aedeagus curved in lateral view, well sclerotized; tegmen with manubrium. Female genitalia: spermatheca partially or well sclerotized; vasculum hook-shaped; ductus moderately long, forming spirals. Spermathecal gland present.

Remarks. Adults of Ogdoecosta species are very similar but can be distinguished with the key below. In Mesomphaliini, adults in some genera show a pronounced sexual dimorphism (e.g. Acromis, see Chaboo 2001); sexual dimorphism may be correlated with male competition behaviors (Borowiec & Świętojańska 2011). Ogdoecosta females are only slightly larger than males. The variability in the spermathecal morphology offers important diagnostic characters and permits discrimination between Ogdoecosta and Chelymorpha . The shape of the spermatheca and ductus are different between those genera.