Solenopsis saevissima species group

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This group was defined by Pitts et al. (2018).



Diagnoses for the gynes, males, and larvae of the non-parasitic species of the S. saevissima species-group are given below. Due to the drastic modification in body form in the social parasites, descriptions of each species are not provided here. Instead, the description of Solenopsis daguerrei serves to distinguish all socially parasitic species from the remainder of the species-group. Solenopsis hostilis has been included in the key for completeness, although no specimens were found during this study and the species apparently has not been collected since its original description. To avoid repeating the descriptive treatment of the workers by Trager (1991), only diagnostic combinations of characters for the major workers are given here.

Gyne.—Head: Usually broader than long, quadrate, wider posterior to eyes than anterior to them, sides weakly convex from eyes to occipital angles, straight to slightly convex ventral to eyes and meeting anterior border of head at a sharp angle. Occipital angles distinctly defined, occiput flat with narrow, shallow median impression. Occipital furrow clearly to weakly defined. Frontal furrow indistinct. Clypeus projecting, carinal teeth very stout and acute, clypeus with anterior shallow concave impression between carinal teeth. Paracarinal teeth small, often poorly defined and, in some cases, absent. Median carinal tooth well developed to indistinct. Mandibles with outer border convex, masticatory border with four teeth, fourth tooth much smaller than others. Eyes large, strongly convex, ovate. Antennal scape in repose reaches or passes lateral ocellus. Antenna with 11 segments (10 segments sometimes in Solenopsis pythia) with 2-segmented club.

Mesosoma: Robust, elliptical, only slightly narrower than head. In lateral view, mesonotum with convex anterior portion that overhangs pronotum and with straight posterior half. Scutellum as high or higher than mesonotum, slightly convex with short perpendicular posterior face, posterior face depressed posteromedially. Angle of propodeum well defined but obtuse, basal face shorter than declivous face. Mesosternum large and subglobose ventrally. Wings hyaline with yellow to brown veins (veins hyaline in S. daguerrei and sometimes in Solenopsis electra).

Metasoma: In lateral view, petiolar node obtusely triangulate, profile of peduncle flattened anteriorly, convex posteriorly. Petiole with median longitudinal carina on anterior 0.50–0.75 of ventral surface. Postpetiole evenly convex. Lateral faces of postpetiole concave to slightly convex. Petiolar and postpetiolar spiracles are tuberculate in some cases. Petiole with basal transverse carina, appears tooth-like in lateral view. In dorsal view, nodes are very strongly transverse, and postpetiole wider than petiole. In cephalic view, petiole sometimes with distinct median lobe, postpetiole broader than high, highest medially.

Male.—Head: Trapezoidal, maximum head width greater than length. Eyes very large, strongly convex, ovate, occupying more than 0.5X side of head, their anterior border almost reaching insertion of mandible. Eyes normally with setae protruding from between ommatidia. Ocelli small to large and prominent, elliptical, lateral ocelli marking boundary of occiput with shallow concave depression between them. Anterior edge of clypeus approximately straight. Clypeus with blunt, central lobe in lateral view. Mandibles small, straight, tridentate, third tooth small, sometimes indistinct. Antennal scape longer than broad, roughly cylindrical. Pedicel subglobose, broad or broader than scape or flagellomeres. First flagellomere >2.0X as long as broad, second flagellomere <1.6X as long as broad, remaining flagellomeres progressively decreasing in width.

Mesosoma: Robust, elliptical, width less than twice that of head. In lateral view, anterior part of mesonotum greatly swollen and overhanging pronotum. Propodeum rounded, declivous face perpendicular and flat except with distinct to indistinct median longitudinal depression, basal face strongly convex transversely and longitudinally. Mesosternum large and subglobose ventrally. Wings hyaline with hyaline to yellow veins.

Metasoma: Node of petiole short in lateral view with acute dorsum; anterior face not sharply separated from thick peduncle, posterior face perpendicular laterally, gently curving medially. In cephalic view, dorsum of node with shallow median impression, sometimes bilobate. Postpetiole in lateral view as high as node of petiole, anterior face, dorsum and posterior face rounded. In dorsal view, both nodes very transverse, postpetiole is approximately 1.0–3.0X as broad as long and as wide as node of petiole. Petiolar and postpetiolar spiracles distinctly tuberculate to not tuberculate. Genitalia strongly retracted. Cuspis laterally flattened, lobate in lateral view and lacking setae. Digitus short and cylindrical, with apical setae and sometimes with lateral setae. Ventral portion of volsellar plate apically produced, clothed with several setae. Ventral surface minutely dentate with rows of triangular teeth. Ventral margin of aedeagus with many anteriorly directed triangular teeth. Aedeagus with anteroventrally directed triangular projection. Apodeme of aedeagus directed perpendicular to slightly obtuse to ventral surface.

Sculpture and Pilosity: Punctures fine and numerous, < 0.001mm wide. Antenna covered with dense, short, white pubescence. Pubescence on legs shorter and stouter than on body.

Fourth instar worker larva.—Head: Antenna with 2–3 sensilla, each bearing spinule. Head setae sparse. Cranial width equal to or slightly broader than long. Labrum small, short, slightly narrowed medially. Mandible heavily sclerotized with two parts: 1) stoutly sickle-shaped body, with three apical teeth not in same plane; 2) straight medial blade forming 0–5 teeth that decrease in size dorsally. Ventral border of labrum weakly concave with ventral corners rounded. Labrum bearing 2–3 coarse isolated spinules near each ventrolateral corner. Maxilla with sclerotized band between cardo and stipes. Labium with patch of spinules dorsal to palpus. Labium with small lateral sclerotized bands. Opening of sericteries a long transverse slit.

Body: Stout. Prothorax bent ventrally at right angles forming very short stout neck. Remainder of body straight. Abdominal diameter greatest at fourth somite. Both ends of body broadly rounded. Dorsal profile of body curved, ventral surface nearly flat. Anus ventral. Leg and wing precursors present. Segmentation indistinct. Integument of ventral surface of thorax and first three abdominal somites with few short transverse rows of minute spinules. Body setae numerous, short, and uniformly distributed. Body setae of two types: 1) simple, slightly curved with alveolus and articular membrane, 4–12 in transverse row on ventral surface of each thoracic somite and anterior abdominal somites; 2) bifid, branches more or less perpendicular to base, tips recurved occurring on various regions of body; often setae posterior to head on thoracic dorsum differ slightly from other setae. Setae on ventral surface with alveolus and articular membrane.

Length: Approximately 2.3–3.8 mm.

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