Systematic Entomology (1984) 9, 373-382 Diagnosis and relationships of the myrmicine ant genus Ishakidris gen .n. (Hymenoptera: Formicidae) BARRY BOLTON Department of Entomology, British Museum (Natural History), London ABSTRACT. The ant genus Ishakidris from Sarawak is described as new. Its relationships with the Brasilian monotypic genus Phalucromyrmex Kempf and the Malagasy monotypic genus f‘ilutruchus Brown are discussed, and the Phala- crumymex genus-group is established to hold the three genera. The resemblances of Zshakidris to the smithistrumiform dacetinegenus Glamyivmyrmex Wheeler and the agroecomyrmecine genus Tatuidris Brown & Kempf are discussed and the similarities are analysed as the results of convergence in the characters concerned. Introduction ‘there is a very strong possibility that Phala- cromyrmex and its undescribed relative may In 1960 Kempf described a remarkable be convergent on the smithistrumiform dace- Brasilian myrmicine ant genus, Phalacro- tines fromsome other part of the Myrmicinae’. myrmex, which bore a striking similarity in The new genus, Ishakidris, is described habitus to the smithistrumiforin dacetines of below and its diagnostic characters listed. The the genus Glamyromyrmex Wheeler. He description is followed by four separate sec- stated in the original description that ‘this tions analysing and discussing its real and new genus seems at least superficially related apparent relationships with the genera Phala- with the ants of the tribe Dacetini’, and cromyrmex, Glamyromyrmex, Tatuidriy and observed that its habitus was reminiscent of Pilotrochus respectively. It is concluded that both Glamyromyrmex and Codiomyrmex Ishakidris shares a genuine close phylogenetic Wheeler. However, after listing the diagnostic relationship with Phalacromyrmex and that characters of Phalacrornyrmex he ultimately these two genera together are most probably decided that ‘it seems best not to include the distantly related to Pilotrochus. A genus- present genus in the Dacetini’, but admitted group is established and defined to hold these that it appeared ‘even farther removed from three genera. The analysis of Glamyromyrmex all other myrmicine tribes’. and Tatuidris indicates that their apparent Bolton (1 983) retained Phalacrornyrmex as similarity to Ishakidris does not reflect a a peripheral dacetine, including it in the syn- genuine relationship but is the result of con- opsis of the dacetine generic distribution and vergence in a number of character-states. enumeration of species, as there seemed no Representatives of all the genera under better placement for it. In the text it was discussion are components of the extensive pointed out that Phalacromyrmex, together tropical leaf litter and topsoil fauna of ants. with a related but undescribed Indo-Australian All appear to be uncommon or rare and most genus, did not fit in any of the recognized sub- species are represented by only very few speci- tribes of the Dacetini, and speculated that mens in museum collections. Phalacromyrmex Correspondence: Mr U. Bolton, 1)epartment of and Tatuidris are exclusively Neotropical, the Entomology, British Museum (Natural History), former known from a single sample collected Cromwell Road. London SW7 SBD. In Brasil, the latter from two samples collected 373 374 Barry Bolton in El Salvador and Mexico respectively. Pilo- sharp longitudinal carina on each side which trochus is represented by a unique worker runs from the ventral base of the mandibular from east central Madagascar and a single insertion to the posterior cuticular lug or worker also constitutes the known representa- flange at the occipital corner. Ventral surface tion of Ishakidris, from the lowland rain- of head with a broadly convex median bulge forests of Sarawak. Glamyromyrmex is more or tumulus. Alitrunk fused, without sutures, widely distributed. With eighteen described the pronotum marginate anteriorly and the species and a number of undescribed species sides marginate throughout their length. In it occurs in the tropical zones of all zoo- profile the propodeal dorsum sloping down- geographical regions, but has a preponderance wards posteriorly to the triangular laminate of species in the Neotropical and Afrotropical propodeal spines, which themselves are sub- regions. tended by, and partially fused with, a broad infradental lamella on each side. Orifice of propodeal spiracle circular, situated close to Ishakidris gem. the posterior margin adjacent to the narrowest point of the propodeal infradental lamellae. DIAGNOSIS OF WORKER. Ants belonging Mesopleuron excavated anterodorsally just to subfamily Myrmicinae. Mandibles massively posterior to the posteroventral corner of the constructed and in profile the convex apical pronotal laterotergite, the excavated area (masticatory) margin almost at a right-angle to containing a semicircular patch of thin cuticle the long axis of the head. Mandibles serially upon which (or embedded in which) are a dentate and opposable, with 12 teeth on each series of radially arranged fine hairs or cuti- apical margin and with the teeth alternately cular processes. From this presumably larger and smaller from base to apex; basal glandular organ a shallow open groove extends series of teeth larger than apical series and the posteroventrally, ending in a slit-like impression mandible lacking a basal lamella. Labrum at the margin of the mesopleuron. In dorsal narrowly long-bilobed anteromedially. Palp view the pronotum much broader than the formula 2,2 (in situ count). Outline shape of mesonotum and propodeum, the last two head in the form of a shield in full-face view separated by a low but sharp transverse carina. (Fig. 2), the occipital corners acute and the Petiole curved-clavate in profile, with a long margin between them concave except for a anterior peduncle and a long low node. Antero- shallow median convexity which encloses a dorsal angle of node blunt but well developed, translucent area of cuticle. Sides of head shal- the dorsum of the node merging evenly with lowly convex and continuous with the frontal the shallowly sloping posterior face, without carinae, the latter massively expanded an- a developed posterodorsal angle. Petiolar teriorly and laterally, fused to the sides of the spiracle small, situated at about the midlength clypeus and completely obscuring the lateral of the peduncle. Ventral process of petiole a parts of the head from full-face view; the low laminar crest which runs the length of the expanded portions of the frontal carinae semi- segment. In ventral view the process seen to translucent. Clypeus broad and broadly be double and narrowly V-shaped, with a inserted between the antennal articulations, laminar crest ventrolaterally on each side of the median portion of the anterior free margin the peduncle diverging posteriorly and meeting evenly convex and prominent. Sites of the anteriorly close to the insertion. First gastral antennal insertions showing through the tergite without a transverse lamellate or expanded flanges of the frontal carinae in full- spongiform crest basally, the petiole, post- face view as a pair of blister-like areas close to petiole and gaster lacking spongiform appen- the anterior margin of the head and abutting dages. First gastral sternite basally with a very the lateral clypeal margins. Antennae with 9 conspicuous broad median flat-topped longi- segments, the apical club of 2 segments. Head tudinal crest which fits between the ventro- in profile with deep antennal scrobes, the eyes lateral flanges of the petiole and the post- small and situated posteriorly within the petiolar laterosternal lobes and restricts the scrobal area close to the ventrolateral margin. degree of anterior flexion of the gaster. Ventrolateral margin of head delimited by a Type-species: Ishakidris ascitaspis sp.n. Myrmicine ant genus Ishakidris 375 Ishakidris ascitaspis sp.n. (Figs. 1-4) shallowly concave when the blades are viewed so that the entire dental row is visible, basally HOLOTYPE WORKER. TL 4.2, HL 1.14, passing through a narrow blunt curve to their HW 1.06, CI 93, ML 0.18, MI 16, SL 0.52, insertions. Mandibles with fine appressed short SI 49, PW 0.50, AL 1.00 (measurements in hairs, the ventral margin on each side with a millimetres, as defined in Bolton, 1983). single very long fine hair close to the articula- Mandibles longitudinally costulate-rugose, tion; this is most probably a mandibular with punctures between the longitudinal com- trigger hair. Anteromedian margin of labrum ponents, the mandibles more densely sculp- with a pair of elongate narrow digitate lobes tured than any other part of the body. which are fringed by narrow lanceolate hairs. Dentition of apical (masticatory) margins Apices of lobes dorsally apparently with a partially obscured by a mesially directed row fused mass of very fine hairs, but this may be of yellowish hairs which arise at the base of an artefact. Dorsum of clypeus and of head the tooth-row down the length of the margin. proper mostly smooth, with minute shallow Counting from the base of the mandible the widely scattered punctures from which tiny first (=basal), third and fifth teeth are approxi- inconspicuous appressed hairs arise. On the mately the same length (c. 0.10) and are the clypeus these tiny hairs are directed towards largest teeth on the margin; teeth 2, 4 and 7 the anterior margin; on the anterior half of are about the same size (c. 0.08); teeth 8 and the head they are directed towards the mid- 10 are reduced to denticles whilst 6,9 and 11 line and on the posterior half they are directed (preapical) are intermediate in size between 5 towards the highest point of the vertex. The and 7; the apical tooth (12) is sharply pointed semitranslucent expanded portions of the and is only slightly smaller than teeth 2,4 and frontal carinae are longitudinally finely arched- 7. Outer margins of mandibles straight to costulate, some of the costulae extending on 3 FIGS. 1-4. Ishakidris asciraspir, holotype worker: 1, body in profile, antennae and legs omitted: 2, head in full-face view; 3, left mandible to show dentition; 4, alitrunk and pedicel segments, dorsal view.