Ogdoecosta Spaeth 1909

Ogdoecosta Spaeth 1909 View in CoL

Ogdoecosta Spaeth 1909: 718 View in CoL

Ogdoecosta juvenca ( Boheman 1854) View in CoL 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 View FIGURE 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 View FIGURE 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 View FIGURE 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 View FIGURE 2 C, D); surface coarsely punctate, pubescent. Labrum prominent, surface smooth with long setae; apical margin emarginated ( Fig. 2 View FIGURE 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 View FIGURE 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 View FIGURE 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 View FIGURE 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 View FIGURE 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.