Discothyrea Roger, 1863

Hita-Garcia, Francisco, Lieberman, Ziv, Audisio, Tracy L., Liu, Cong & Economo, Evan P., 2019, Revision of the Highly Specialized Ant Genus Discothyrea (Hymenoptera: Formicidae) in the Afrotropics with X-Ray Microtomography and 3 D Cybertaxonomy, Insect Systematics and Diversity 5, pp. 1-84 : 8-9

Discothyrea Roger, 1863

Nomenclature

Discothyrea Roger, 1863 . Type-species: Discothyrea testacea , by monotypy.

Prodiscothyrea Wheeler, 1916 . Type-species: Prodiscothyrea velutina , by monotypy.

[Junior synonym of Discothyrea by Brown, 1958a] Pseudosysphincta Arnold, 1916 . Type-species: Pseudosysphincta poweri , by monotypy. [Junior synonym of Discothyrea by Brown, 1958a]

Pseudosphincta Wheeler, 1922. [incorrect subsequent spelling]

Worker Description

Head usually longer than broad, less often approximately as long as broad and subquadrate; posterior head margin transverse to gently rounded; sides of head subparallel, converging anteriorly, or rounded in frontal view; anterolateral corners of gena rounded, squared, or sharply angulate to denticulate; clypeus and frons completely fused, epistomal sulcus absent; clypeus anteriorly produced, overhanging mandible, with anteromedial disc rectangular, convex, sagittate, or weakly emarginate, or anteriomedial disc of clypeus deeply concave, impressed and ventral to anteromedial frontal projection; lateral area of clypeus narrow, concave between antennal sockets and anterolateral corner of gena; frons anteromedially prolonged such that antennal sockets located anterad anterior tentorial pits; frontal carinae anteromedially fused, posteriorly variously modified: as a broad, elevated plate, rhomboid in frontal view, extending from anterior clypeal margin to posterior third of head, forming deep scrobal areas; as a short but broad rhomboid to triangular swelling not reaching midline of head; or as a thin lamella, disciform, lobate, or triangular in profile, sometimes slightly broadened anteromedially, lamella often thinnest basally, sometimes with a distinct translucent fenestra. Antenna with 6–11 antennomeres; scape slightly to strongly incrassate apically and typically not surpassing posterior head margin; apical antennomere greatly enlarged, forming a swollen club usually about as long as remaining flagellomeres taken together; subapical flagellomeres highly compressed, one to five flagellomeres proximal to antennal club with both distal and proximal margins deeply invaginated, forming two sclerotic annuli internally per subsegment, first few flagellomeres extremely compressed and externally indistinct, variably overlapping. Compound eye variably present, welldeveloped with multiple ommatidia, globose and protruding from head, eye setose; or eye small and flattened, ommatidia indistinct; or eye reduced to a pigmented spot; or eye entirely absent. Mandible with masticatory margin edentate, or with a distinct subapical tooth, denticle, or swelling, and/or with a subbasal angle or denticle, basal angle of mandible rounded, squared, or angulate, sometimes sharply; ectal face of mandible usually with carina confluent with masticatory margin for some of its length, leaving a smooth, depressed mesal region where it diverges from margin that includes subbasal angle or denticle when present; mesal face of mandible asetose, or with prominent row of enlarged setae, setae stout and sometimes apically flattened. Ventral head surface with raised, welldefined postocciput, sometimes with an anteromedial carina; with or without raised, rounded tumuli and flattened, unsculptured posterolateral areas. Palpal formula variable: 6,4; 5, 4; 4,4; 4,3; 4,3; 1,3 (see Note below); secondary maxillary palpomere tubular, not hammer-shaped; first two proximal maxillary palpomeres highly reduced, partially fused, and transverse in relation to one another, such that the second palpomere articulates perpendicular to the first and third palpomeres in a zigzag arrangement.

Mesosoma variable in shape, gracile to very stocky and robust; usually moderately rounded or posteroventrally sloping in profile but rarely strongly convex, high-rounded; in dorsal view mesosoma subrectangular to strongly narrowed posteriorly; pronotal humeri rounded; promesonotal junction fused, suture entirely absent or very rarely scarcely detectable; pronotomesepisternal junction sutured, unfused; median mesepisternal sulcus absent; posterolateral corners of propodeum unarmed and rounded to strongly angulate or with distinct denticles; declivitous face of propodeum sloping to strongly concave, sometimes finely marginate; propodeal spiracle without bulla, atrial opening round to oval, usually located at or slightly ventrad mid-height of propodeum; propodeal lobes present, short and truncate to lobate or flangelike; metapleural gland present.

Legs usually short, sometimes somewhat elongate; mesotibia variably unarmed, or with an apicoventral seta inserted in a pit, or with a distinct apicoventral spur; mesobasitarsus sometimes very elongate, as long as remaining tarsomeres taken together.

Petiole variable in shape; outline of anterior face nearly round, disciform, rectangular, roughly or distinctly hexagonal, or often clearly pentagonal; dorsal margin of anterior face flat, weakly to strongly rounded, concave, or peaked, sometimes strongly so; anterior face of petiolar node flat, weakly concave, or strongly concave, sometimes most strongly excavate medially such that node almost bilobed; petiolar node often dorsally attenuated and posterodorsally sloping; petiole narrow to very thick anteroposteriorly; in dorsal view petiolar node rectangular to rhomboid, sides parallel to strongly diverging posteriorly; petiolar spiracles opening ventrally, spiracular openings large and round, elliptical, or reniform; anterior disc of petiolar sternite entire, undivided; subpetiolar process variable, from a very small, rounded disc to a strongly projecting, digitate to triangular lobe, when well-developed often with a posteromedial groove at the attachment of the process to the sternite.

Abdominal segment 3 either much longer than abdominal segment 4, subequal in length, or clearly shorter; helcium axial; segment overall roughly campaniform, typically widest just anterad posterior margin; abdominal tergite 3 slightly to strongly prolonged anteriorly past anterior edge of sternite; abdominal sternite 3 concave, sloping, or rounded in profile, with a somewhat distinct to very distinct anterior face, anterior face posteriorly depressed, ventral face with a distinctly elevated anterior border, anterior border flat to deeply concave in ventral view, border variably smooth or with prora, prora narrowly carinulate to strongly raised, either following curvature of border or forming a distinct, rectangular medial plate; abdominal sternite 3 variably evenly increasing in depth posteriorly, with a broad and smooth but differentiated posteromedial lobe, with a broad medial ridge widening to a lobe posteriorly, or with medial ridge narrow and carinate anteriorly; when present, medial carina in profile rounded or squared with distinct anterior face, carina sometimes anteriorly surpassing prora.

Abdominal segment 4 vaulted, roughly to clearly in the shape of a quarter-sphere; abdominal sternite 4 anteriorly either overall sloping to rounded, with a small groove accommodating the posterior margin of abdominal sternite 3, or nearly right-angled, forming a large lip overlapping the posterior margin of abdominal sternite 3.

Sculpture highly variable, but often predominantly punctatereticulate to foveolate-reticulate or alveolate to areolate; sculpture of abdominal segment 4 typically reduced relative to abdominal segment 3.

Setation variable but unspecialized except for mandibular setae when present.

[Note: all values of palp formula besides 6,4 ( Keller 2011) are from Sosa-Calvo and Longino (2008). Keller (2011) noted that this apparent diversity of counts could be due to miscounting and we concur.]

Afrotropical Species Complexes

In this study, we focused on the material from the Afrotropics available to us. As noted above, Brown (1958a) already grouped the then-known species of Discothyrea into two complexes. Our examinations clearly confirm the D. oculata and D. traegaordhi complexes since they are significantly divergent in their respective morphology ( Fig. 5 ). However, on the basis of preliminary analyses of limited material from other regions, we are confident that there at least one or two more complexes found in the Indo-Malayan region and Oceania. We do not define or discuss them in detail due to the scarcity of material available to us and the focus of this study on the Afrotropical region.

Figures

Fig. 5. Still images from surface display volume renderings displaying the general morphology of both species complexes. Discothyrea oculata complex, D. mixta (CASENT0285473): (A) head in full-face view, (B) head in profile, (C) head in ventral view, (D) body in profile. Discothyrea traegaordhi complex, D. wakanda (CASENT0790326): (E) head in full-face view, (F) head in profile, (G) head in ventral view, (H) body in profile.