Iridomyrmex Mayr

Heterick, Brian E. & Shattuck, Steve, 2011, Revision of the ant genus Iridomyrmex (Hymenoptera: Formicidae) 2845, Zootaxa 2845 (1), pp. 1-174 : 18

Iridomyrmex Mayr

Iridomyrmex Mayr, 1862: 702 . Type species: Formica detecta Smith, 1858 by subsequent designation of Bingham, 1903: 297

Worker Diagnosis. The anterior margin of the clypeus above the mandibles is usually highly modified with convex areas towards the sides and a central projection (this central projection, hereafter termed the anteromedial clypeal prominence, varies from strongly to weakly developed in most Iridomyrmex , but is absent in I. mirabilis sp. n. and vestigial and barely noticeable in several species related to I. calvus and I. brunneus ). The compound eyes are placed relatively high on the head and away from the mandibles ( Shattuck, 1992b , fig. 95). Most other genera in this subfamily have the anterior margin of the clypeus weakly convex, straight or weakly concave. Only Froggattella and Philidris share the anteromedial clypeal prominence with Iridomyrmex , but these have the eyes low on the head, nearer to the clypeus and Froggattella has the propodeal spiracle higher and on the propodeal spines.

Worker Description. Head. Posterior margin strongly convex to strongly concave. Compound eyes present, generally oval, with slightly to strongly lobate inner margin, eye may also be narrower posteriad than anteriad; eyes located relatively posteriorly on head. Ocelli normally absent but one or more ocelli may be present in some species. Antenna 12-segmented. Scape short to long, surpassing posterior margin of head by maximum of about one half of its length, but failing to attain posterior margin in several species. Anterolateral clypeal margin posterior to mediolateral region, and separated from it by a shoulder. Anteromedial margin usually with a sharp to weak central prominence, sometimes straight (several species related to I. calvus and I. brunneus ). Posterior clypeal margin between the anterior and posterior surfaces of the antennal socket cavities. Anterior tentorial pit nearer the antennal socket than the mandibular insertion. Frontal carinae present. Anterolateral hypostoma reduced to a thin sclerite. Median hypostoma entire. Psammophore usually absent, but some arid area species with many curved, erect setae in gula region. Mouthparts. Palp formula 6,4. Third maxillary palp segment subequal in length to segment 4 (except in I. trigonoceps ). Fifth maxillary palp segment situated apically. Mandible of more-or-less uniform appearance across all species, usually with 7–10 teeth and 2–5 denticles. Apical tooth longer than subapical tooth. Basal angle distinct or indistinct, basal margin denticulate distally, smooth proximally. Mesosoma. Spines absent from all surfaces. Posterior pronotum planar, rounded or angled. Mesothoracic spiracles opening on small dorsal prominences in some species. Mesopleural process absent. Anteromedial mesosternum even with lateral regions. Dorsal face of propodeum may be uniformly convex to flat, abruptly conical, or convex anteriad and flattened posteriad. Propodeal angle commonly absent, but may be sharply defined and even (rarely) acute. Declivitous face of propodeum convex to flat, longer to shorter than dorsal face. Metanotal groove always present and forming a weak to strong angle between the mesonotum and propodeum. Propodeal spiracle nearly always lateral and ventral of the propodeal surface, rarely located at propodeal angle or immediately adjacent to declivitous surface. Erect setae on mesosoma 0–80 plus, appressed pubescence sparse to dense. Petiole. Node present (present as angle in I. mirabilis ), usually squamiform, but may be thicker, even approaching subcuboidal when viewed in profile. Dorsum of node generally rounded, rarely angulate or even acuminate. In profile, node usually angled anteriad, with anterior face subequal to or slightly shorter than posterior face, but anterior face may be much shorter than posterior face, the posterior face curved in several species. Petiole with or without a ventral lobe. Gaster. First tergite usually vertical and not concealing the petiole in dorsal view, with or without a groove or indentation for receiving the basal portion of the petiole: however, in several species related to I. calvus the first gastral tergite is arched posteriad away from the node. Anterior tergosternal suture extends laterally from helcium in a distinct arch which extends dorsal of the dorsal helical surface. Gastral compression usually absent, but dorsoventral compression evident in I. mirabilis . Legs. Mesotibia with one spur, which varies from simple to pectinate; metatibia with one pectinate spur. General characters. Worker caste mostly monomorphic, rarely polymorphic. Integument thin and flexible, sculpture mainly limited to fine punctation or microreticulation. Proventriculus. Cupola much broader than bulb; round with short pile; smooth, without sculpture; and with narrow phragma. Bulb completely hidden by cupola in lateral view. Longitudinal muscle No.1 absent. Occlusory tract absent.