Discothyrea mixta

Discothyrea mixta is better represented in collections than Discothyrea oculata and most species of the traegaordhi complex, which may suggest lifestyle differences, making them more amenable to discovery, or be indicative of truly greater abundance. The species is known from a variety of forest habitats at different elevations throughout most of the Afrotropical region.

In foraging experiments, Dejean et al. (1999) found that D. mixta only accepted spiderlings and spider eggs as prey items. They rapidly consumed the spiderlings while often storing the eggs as a long-term resource. These findings are supported by unpublished observations made on a nest collection in Kibale Forest, Uganda, which revealed a large number of unidentified, rounded eggs, presumably of spiders.

Identification
Hita-Garcia and Lieberman (2019) - Discothyrea mixta differs from the only other member of the Discothyrea oculata species complex, D. oculata, by the following combination of characters:
 * smaller species (WL 0.59–0.72)
 * broader head (CI 88–94)
 * smaller eyes (OI 5–9)
 * propodeum strongly angulate to denticulate
 * declivitious face of propodeum without costae or rugae
 * propodeum dorsally and laterally finely marginate
 * shorter legs (HFI 62–68)
 * AT4 roughly sculptured, striate to punctate
 * scrobal area alveolate to punctate posterolaterally, becoming striulate to strigulate medially

In general, the separation of D. mixta from D. oculata is very easy and both are difficult to mistake for each other. They differ in body size, eye size, and location on the head, as well as the shape of the propodeum and the sculpture on the propodeal declivity.

Discothyrea mixta varies slightly in overall size (WL 0.59–0.72), number of ommatidia, and coarseness of sculpture. Frequently, the sculpture of the lateral mesosoma is somewhat reduced, and the propodeal carinulae can vary slightly in shape and distinctness. The length, abundance, and stature of pilosity are somewhat variable, forming a more or less distinct dorsal layer on the mesosoma and abdominal terga. Nevertheless, considering the extremely wide distribution of D. mixta, this observed intraspecific variation is not surprising and even lower than one might expect.

Distribution based on Regional Taxon Lists
Afrotropical Region: Angola, Cameroun, Democratic Republic of Congo, Ghana, Ivory Coast, Kenya, Liberia, Mozambique, Rwanda, South Africa, Uganda, United Republic of Tanzania.

Nomenclature

 * . Discothyrea mixta Brown, 1958g: 343, figs. 47, 48 (w.) LIBERIA.
 * Type-material: holotype worker, 4 paratype workers.
 * [Note: Brown, 1958g: 344, records that 1 paratype was destroyed during dissection.]
 * Type-locality: holotype Liberia: Bolahun (J.C. Bequaert); paratypes with same data.
 * Type-depositories: MCZC (holotype); MCZC, MHNG, USNM (paratypes).
 * Status as species: Leston, 1971: 117; Bolton, 1995b: 171; Hita Garcia, et al. 2013: 222; Hita Garcia, Lieberman, et al. 2019: 18 (redescription).
 * Distribution: Angola, Cameroon, Central African Republic, Democratic Republic of Congo, Ghana, Ivory Coast, Kenya, Liberia, Mozambique, Rwanda, South Africa, Tanzania, Uganda.

Worker
Hita-Garcia and Lieberman (2019) - (n = 10) EL 0.04–0.07; HL 0.63–0.75; HW 0.57–0.68; SL 0.40–0.50; PH 0.31–0.40; PW 0.43–0.53; DML 0.35–0.50; PrH 0.39–0.50; WL 0.59–0.72; HFL 0.38–0.49; PeL 0.10–0.13; PeW 0.30–0.33; PeH 0.28–0.35; LT3 0.54–0.79; LT4 0.27–0.41; OI 5–9; CI 88–94; SI 64–69; LMI 51–56; DMI 68–75; DMI2 107–121; ASI 46–58; HFI 62–68; DPeI 250–313; LPeI 240–313.

Head very broad (CI 88–94), posterior head margin strongly convex, evenly curving into sides, posterodorsal corners of head indistinct; in frontal view sides of head convex, slightly concave between eye and anterolateral corner of gena; eyes small but well developed, setose (OI 5–9), comprising around ten small ommatidia; ommatidia globose, silvery, eyes protruding from head; eyes situated laterally on gena, slightly anterad halfway between anterolateral corner of gena and posterior head margin; frontal carinae produced as broad, elevated plate; rhomboid in frontal view, extending to around posterior third of head, widest point at around anterior eye margin, broad at posterior attachment to head, pointed anteriorly; in profile rooflike, forming broad, deeply depressed scrobal area extending to just anterad eye; anteromedially fused and reduced to thin, translucent septum between antennal sockets; posterolateral portion of torulus flangelike; torulus reduced posteromedially, thus confluent with deep, exposed antennal acetabulum; scrobe mostly strigulate, becoming punctate closer to eyes, merging with alveolate sculpture of head at scrobal margin; medial clypeus rectangular, short, anterior margin transverse, bearing very dense layer of appressed to decumbent white pilosity; sides of medial clypeus subparallel laterad antennal sockets. Antenna with moderately long scape (64–69), scape somewhat expanded apically, slightly bent; pedicel a short cylinder, broader than long; true antennomere count eleven; apparent antennomere count nine to eleven; flagellomeres basad apical club highly compressed, taken together approximately as long as apical club. Ventral head surface with two low, somewhat indistinct rounded tumuli situated laterally, slightly posterad midline (in profile); postoccipital ridge with well-developed anteromedial carina, extending about a one-third of the way between occipital foramen and posteromedial extent of hypostoma; medial region of hypostoma semicircular to a low triangle, apex somewhat rounded, hypostomal arms somewhat narrowed, arms expanded slightly apicolaterally; palpal formula not examined. Mandible edentate; basal angle rounded; with blunt prebasal angle; ectal face with longitudinal carina extending from prebasal angle to apex, carina becoming confluent with masticatory margin apically, leaving long comma-shaped, depressed, smooth medial region on masticatory margin.

Mesosoma robust, evenly convex, pronotum scarcely higher than propodeum; in dorsal view mesosoma relatively broad and stout (DMI 68–75; DMI2 107–121) and distinctly narrowed posteriorly, pronotum distinctly wider than propodeum; pronotal humeri obliquely rounded; posterior propodeal margin straight; posterodorsal corners of propodeum strongly angulate to denticulate, angles subtended and medially joined by narrow carinulae, thus propodeum laterally and dorsally marginate; in posterior view, carinulae forming two arches, shaped like an inverted lowercase omega, medially joining as unpaired carina traversing declivitous face; declivitous face of propodeum distinctly concave in profile and oblique posterior view; propodeal spiracle small and indistinct, directed posterolaterally; propodeal lobes very short and blunt.

Legs quite long (HFI 62–68) and robust; mesotibia with short but distinct apicoventral spur.

Petiolar node thickly disciform, not attenuated dorsally, about 2.4 to 3.2 times higher than broad (LPeI 240–313); in profile anterior face of node distinctly convex, curving smoothly over dorsum, without distinct apex; posterior face of node vertical; in dorsal view, node roughly a rounded trapezoid, sides strongly diverging posteriorly, anterior margin convex, posterior margin concave, about 2.2 to 3.2 times broader than long (DPeI 215–313); in anterior view, petiolar outline subcircular; in oblique anterodorsal view with weak median concavity; in ventral view, a narrow trapezoid, sides diverging strongly posteriorly; subpetiolar process short, lobate to subquadrate.

Abdominal segment 3 asymmetrically campaniform, tergite evenly convex, widest posteriorly; AS3 somewhat flat to bulging posteriorly, deepest posteriorly, with concave, mostly unsculptured anteromedial region bordered anteriorly by sharply carinate, laterally narrow prora; AT3 approximately 1.9 to 2.2 times longer than AT4 (ASI 46–58); AT4 hemidemispherical to semicylindrical, gently recurved, spiracle sometimes exposed, small but prominent; successive abdominal segments short, telescopic, often concealed.

Sculpture on head, mesosoma, petiole, and abdominal segment 3 alveolate, alveoli giving rise to one or several setae; coarseness of sculpture somewhat variable, equivalently developed on all tagma, or often weakest on lateral mesosoma; ventral head surface posteromedially unsculptured; scape densely punctate; declivitous face of propodeum smooth except for fine medial carina; AT4 densely punctate, punctae usually more distinct posterolaterally; mandibles with numerous piligerous punctae.

Setation fairly consistent on dorsal surfaces of head, mesosoma, and petiole, a dense layer of appressed to erect white setae; gena and lateral mesosoma sometimes with sparser setation; density and length of setae somewhat variable between individuals; scrobal area glabrous and shining; AT3 evenly setose over its dorsal and lateral surfaces, setation shorter and less dense than on mesosoma, not forming distinct dorsal layer; AT4 with long, abundant, fine appressed pubescence and dense dorsal layer of decumbent to erect pilosity; successive abdominal segments with dense, flocculent, erect yellowish setae; ectal face of mandible with fine, curved, appressed to decumbent setae; with row of stout, spatulate setae on mesal face of masticatory margin; legs with fairly dense but relatively fine and entirely appressed white pubescence.

Color testaceous- to luteous-orange; legs and abdominal segments III–VII often bright orange to yellowish, lighter than rest of body.

References based on Global Ant Biodiversity Informatics

 * Belshaw R., and B. Bolton. 1994. A survey of the leaf litter ant fauna in Ghana, West Africa (Hymenoptera: Formicidae). Journal of Hymenoptera Research 3: 5-16.
 * Belshaw R., and B. Bolton. 1994. A survey of the leaf litter ant fauna in Ghana, West Africa (Hymenoptera: Formicidae). Journal of Hymenoptera Research. 3: 5-16.
 * Bolton B. 1973. The ant genera of West Africa: a synonymic synopsis with keys (Hymenoptera: Formicidae). Bulletin of the British Museum (Natural History). Entomology 27: 317-368.
 * Brown W. L., Jr. 1958. Contributions toward a reclassification of the Formicidae. II. Tribe Ectatommini (Hymenoptera). Bulletin of the Museum of Comparative Zoology 118: 173-362.
 * Hita-Garcia F., Z. Lieberman, T. L. Audisio, C. Liu, and E. P. Economo. 2019. Revision of the highly specialized ant genus Discothyrea (Hymenoptera: Formicidae) in the Afrotropics with X-ray microtomography and 3D cybertaxonomy. Insect Systematics and Diversity 3(6): 5:1-84.
 * Huong N. T. T., P. V. Sang, and B. T. Viet. 2015. A preliminary study on diversity of ants (Hymenoptera: Formicidae) at Hon Ba Nature Reserve. Environmental Scientific Conference 7: 614-620.
 * Lévieux J. 1972. Les fourmis de la savane de Lamto (Côte d'Ivoire): éléments de taxonomie. Bulletin de l'Institut Fondamental d'Afrique Noire. Série A. Sciences Naturelles 34: 611-654.
 * Ross S. R. P. J., F. Hita Garcia, G. Fischer, and M. K. Peters. 2018. Selective logging intensity in an East African rain forest predicts reductions in ant diversity. Biotropica 1-11.