Systematic Entomology (1984) 9, 373-382

Diagnosis and relationships of the myrmicine Ishakidris gen .n. (: 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 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 ’. 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 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 , 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. 25 376 Barry Bolton to the head proper on each side of the median spatulate hairs, and with another pair postero- convexity. Sides of head behind level of frontal laterally. On the postpetiole there is a similar carinae with 3 pairs of short acute laterally pro- pair of hairs anterodorsally, two pairs postero- jecting hairs, otherwise the cephalic dorsum dorsally and two pairs laterally. Petiole node without standing pilosity of any description. in dorsal view longer than broad, broadening Occipital margin bounded by a low but sharply from front to back; postpetiole broader than defined carina which ends in a pair of trans- long, subrectangular, margined by thick rugae lucent cuticular flanges or lugs running down anteriorly and laterally and with a more the posterolateral occipital lobes. Ventrally dorsally situated pair of longitudinal rugae these lugs are confluent with the ventrolateral which weakly converge posteriorly. Latero- longitudinal carinae which run forwards to sternites of postpetiole densely punctate. First the bases of the mandibles. Eyes small, with gastral tergite finely superficially reticulate only 7 -8 ommatidia, the maximum diameter everywhere, without pilosity and with a few 0.06 (c. 0.06~HW). Sides of head between short but sharply defined basal costulae eye and mandibular base finely irregularly arising from the slightly thickened basal margin. rugulose with roughened to punctulate spaces First gastral sternite smooth and convex, the between the rugulae. Above the eye the rugu- broad basal carina thin-walled and translucent lac fading out and behind the eye the sides of close to the base of the sclerite; the true basal the head mostly smooth. A secondary longi- surface of the sternite concave and thickly tudinal rugule or weak carina runs from near sclerotized below the postpetiole. Apex of the mandibular base to a point well behind the gaster with a few inconspicuous projecting level of the eye, and is situated between the hairs. Femora and tibiae of middle and hind eye and the carinate ventrolateral cephalic legs with appressed narrowly spatulate hairs. margin. Bulging convex ventral surface of Colour of head, alitrunk and pedicel segments head smooth and shining. Antenna1 scapes and glossy medium brown to reddish brown, the funiculi clothed with decumbent or appressed frontal carinae, antennae, legs and gaster narrowly spatulate hairs. With the alitrunk in lighter brown to yellowish brown. Mandibles dorsal view the humeri rounded, the lateral darker in colour than head-shield; margina- marginations darker in colour than the dorsum tfons of head ventrolaterally and of alitrunk proper, the surface lacking standing hairs laterally blackish. except for a single pair on the transverse ridge Holotype worker, EAST MALAYSIA: separating the mesonotum and propodeum. A Sarawak, 4th Division, Gunong Mulu National narrow arcuate ridge between the propodeal Park, v-viii.1978, litter sample Camp 5 spines separates the dorsum from the declivity. (f? M. Hamrnond & J. E. Marshall) (BMNH). Dorsum of alitrunk mostly unsculptured, with one or two faint longitudinal rugulae on each side of the mesonotum which run forward on Co m m en ts to the posterior pronotum. Both pronotum and mesonotum with a few scattered minute The holotype is damaged, lacking its left appressed hairs arising from shallow pits, as middle and hind legs which were missing on on the head. Anteromedially the pronotum collection. with a very short low carina. Propodeal de- The single known specimen of I.ascitaspis clivity between the infradental lamellae was recovered from a Winkler bag sample of exceedingly finely punctulate. Sides of ali- previously sieved leaf litter collected at Camp trunk glossy and smooth, the propodeal 5 in Gunong Mulu National Park during the infradental lamellae showing an internal fine Royal Geographical Society expedition there reticular patterning. Petiole with sides and in 1978. Camp 5 lay beside the Melinau River dorsum of node rugose, the rugae less well in lowland rainforest at the edge of the lime- defined dorsally than laterally. Laminar stone outcrop which slopes up to the spec- ventral crest of petiole reticulate-punctate as tacular Limestone Pinnacles of the park. is the area below the level of the spiracle. Diagnostic characters which in combination Dorsurn of petiole node with one anterior isolate fshakidris from the workers of all and two posterior pairs of short narrowly other myrmicine ant genera are as follows. Myrmicine ant genus Ishakidris 317

1. Form and dentition of the massive mandibles a sample of topsoil taken at IbicarC, Santa and their lack of a basal lamella (Fig. 3). Catarina State. This species shows a marked 2. Palp formula 2,2. similarity in habitus to Ishakidris and also 3. Labrum anteriorly with a pair of elongate digi- shares the following suite of apomorphic tate lobes. characters. 4.Antennae with 9 segments, the two apical seg- ments forming a strongly defined club (Fig. 2). 1. Mandibles massive and strongly downcurved in profile. 5. Antennal scrobes deep and extensive, the eye situated ventrolaterally within the scrobal area 2. Mandibles with alternating large and small teeth (Fig. 1). down the length of the masticatory margin. 6. Head shield-like, the frontal carinae very widely 3. Apical tooth of mandible not clearly the largest separated and greatly expanded anteriorly and on the masticatory margin. laterally (Fig. 2). 4. Labrum narrowly bilohate. 7. Frontal carinae flanking lateral portions of cly- 5. Palp formula 3,2 or 2,2. peus and forming the anterolateral corners of 6. Frontal carinae very strongly expanded anteriorly the head (Fig. 2). and laterally. 8. Mesopleural presumed glandular area present, 7. Frontal carinae flanking clypeus laterally and with subtending open groove (Fig. 1). farming the anterolateral angles of the head. 9. Petiole and postpetiole lacking spongiform or 8. Antennae with less than 12 segments. lamellate appendages (Figs. I, 4). 9. Antennal club of two enlarged apical segments. 10. Massive longitudinal basal carina present on first 10. Antennal scrobes deep and extensive. gastral sternite (Fig. 1). 11. Eyes situated ventrolaterally within the scrobal area. Relationship with Phalacromymex Kempf 12. Alitrunk flattened dorsally and marginate (Figs. 5-7). laterally. 13. Propodeal spiracle close to margin of decivity The singie species of the Brasilian genus (discounting the propodeal infradental lamellae). Phalacromyrrjzex, P.fugax Kempf, is known 14. Propodeal spines laminate and subtended by from a short series of workers recovered from infradental lamellae.

FIGS. 5-7. PhuiUcromyrmru pgux Kempf, paratypc worker: 5, body in profile, antennae and legs omitted; 6, head in full-face view; 7, left mandible to show dentition. 378 Barry Bolton

15. Mesonotum and propodeum much narrower than The similar habitus and wealth of detailed pronotum. correspondence in specialized characters be- 16. Middle and hind legs lacking tibial spurs. tween Phalacromyrmex and Ishakidris leads [The assumed plesiomorphic states for these to the conclusion that a true phylogenetic characters at this level of analysis are: 1. Man- relationship, rather than a strong convergence, dibles relatively slender and feebly down- is indicated here. Particularly convincing are curved; 2. mandibles with teeth regularly the remarkable specializations shown. by the decreasing in size from apex to base; 3. apical head and mandibles, and the construction of tooth the largest on the masticatory margin; the antennae. 4. labrum simple to weakly medially indented ; Characters which differentiate the two 5. palp formula > 3,2 (to a maximum at PF genera are as follows. 6,4); 6., 7. frontal carinae absent; 8. antennae Ishakidrik Phalacromywnex with 12 segments; 9. antennae filiform; 10. Antenna with 9 Antenna with 11 antenna1 scrobes absent; 11. eyes lateral; 12. segments segments alitrunk transversely convex, immarginate; Mandibles with 12 teeth Mandibleswith 10 teeth Palp formula 2,2 Palp formula 3,2 13. propodeal spiracle approximately at mid- Occipital corners Occipital corners length; 14. propodeal spines not laminate; acute in full-face rounded in full-face 15. mesonotum and propodeum subequal to view view pronotum in width; 16. pectinate tibial spurs Ventrolateral margins Ventrolateral margins of head carinate of head not carinate present on middle and hind legs. These assumed Pronotal humeri Pronotal humeri plesiomorphic states are abstracted from the rounded angulate conditions presently thought to accord most Mesopleural presumed Meso pleural presumed accurately with the hypothetical ancestral glandular area sub- glandular area sub- condition of the myrmicine ants, and assumes tended by an open tended by a series of groove oblique costulae that the subfamily Myrmicinae constitutes a Base of first gastral Base of first gastral holophyletic taxon.] sternite carinate sternite not carinate

FIGS. 8-10. GZamyromyrmex workers: 8, G.terragnarhus (Taylor), body in profile, antennae and legs omitted; 9, G:afn'canus Bolton, holotype, head in full-face view; 10, G.sisrrurus Bolton, paratype, left mandible to show dentition. Myrmicine ant genus Ishakidris 379

Relationship with Ghmyromyrmex Wheeler myrmex. The anterodorsal excavation of the (Figs. 8- 10) mesopleuron, just behind the posteroventral Among the smithistrumiform dacetines some corner of the pronotal laterotergite, is always members of the genus Glamyromyrmex show present and sometimes has a few short hairs a most striking habitus resemblance to Isha- traversing it (thus in G.sistrurus Bolton, cryp- kidris and Phalacromyrmex, especially to the turus Bolton, tetragnathus (Taylor), dagon former as can be seen by comparing Figs. 1-3 Bolton, sahurus Bolton, tukultus Bolton, with Figs. 8-10. In the Glamyromyrmex thuvidus Bolton, and an undescribed species figures G.tetragnathus (Taylor) (Fig. 8) and from Paraguay). In other species the excava- G.africanus Bolton (Fig. 9) have been selected tion is present and traversed by numerous specifically because of their habitus similarity hairs, but is not subtended by a groove (G. to Ishakidris, other species are not nearly so semicomptus (Brown), aztecus Kempf, excisus like I.ascitaspis in general appearance. The (Weber), and an undescribed species from mandible of G.sistrurus Bolton (Fig. 10) is in Sarawak). In an undescribed species from Hong reality very strongly arched-downcurved but Kong the mesopleural impression is well has been drawn here as if flat so that the entire developed and fringed with fine flocculent dental array can be seen, and is thus semi- material. Given this variation of development diagrammatic; the prominent large basal in Glamyromyrmex (and in some other lamella, characteristic of the genus, is stippled. smithistrumiform genera), and the correspond- Eighteen species of Glamyromyrmex have ing amount of variation in this supposed been described from the Neotropical and Afro- glandular structure in other genera of similar tropical regions, and further undescribed habitus, where it is small in Phalacromyrmex, species are known from the Oriental and Indo- moderately developed in Ishakidris and very Australian regions. It is suspected that a few large and subcircular in Pilotrochus, it seems species from Australia and the Neotropics most likely that it has developed independently which are presently placed in Codiomyrmex several times and cannot be utilized in assess- Wheeler may also really belong in Glamyro- ing the relationships of these genera. myrm ex. In spite of the characters listed above I Apart from habitus similarity the following consider the apparent similarities between characters also correspond in Ishakidris and Ishakidris and Glamyromyrmex to have been Glamyromyrmex workers. acquired convergently, and view the resem- 1. Apical mandibular tooth is not the largest. [In blances as superficial. This conclusion is Gsistrurus, illustrated in Fig. 10, teeth 4 and 5 justified by a comparative analysis of the in front of the basallamella are the largest. There diagnostic characters of Ishakidris with all is some variation in Gkzmyromymex in size- distribution of teeth but in general one of the the eighteen presently recognized species of basal series of five teeth, which follow the basal Glamyromyrmex, tabulated below. lamella, is the largest on the masticatory margin. 1 Ishokidris Clamyrom yrmex 2. Mandibles massive and bear trap-like, strongly 1. Teeth alternating in Teeth not alternathg arched-downcurved and at least in part at a size down the length in size down the length right-angle to the long axis of the head. of the mandibular of the mandibular 3. Labrum bilobate. masticatory margin masticatory margin 4. Antenna1 club of two segments. 2. Mandibles without a Mandibles with a basal 5. Frontal carinae widely separated and strongly basal lamella (Fig. 3) lamella (Fig. 10) expanded to form a shield-like head m full- 3. Clypeus in full-face Clypeus in full-face view face view. view not forming a forming a part of the 6. Extensive deep antenna1 scrobes present. part of the side of side of the head in 7. Eyes small and situated ventrally within the the head in front of front of the frontal scrobal area or on the ventrolateral margin. the frontal carinae carinae (Fig. 9) 8. Propodeal spiracle set close to the margin of the (Fig. 2) declivity (not counting any infradental lamellae 4. Lateral clypeal margins Lateral clypeal margins which may be present). flanked by the not flanked by the The supposedly glandular area of the meso- expanded frontal expanded frontal carinae, which form carinae, the clypeus pleuron, well defined and subtended by a the anterolateral angles forming the antero- posteroventrally directed open groove in of the head lateral angles of the Ishakidris, is variously developed in Glamyro- head 380 Barry Bolton

5. Palp formula 2,2 Palp formula 1,1 part of the diagnosis of the smithistrumiform 6. Antennae with 9 Antennae with 6 genus-group or of the Dacetini as a whole. segments segments Character 1 is the only remaining corres- 7. Ventral surface of head Ventralsurface of head pondence, but the reduced apical tooth without a transverse with a transverse appears almost certainly acquired convergently post-buccal impression post-buccal impression as the mandibles have no other correlating 8. Mandibular trigger hairs Mandibular trigger hairs on ventral bases of on apices of labral detailed structures. mandibles lobes These considerations imply most strongly 9. Petiole and postpetiole Petiole and postpetiole that the apparent similarity of Ishakidris and without spongiform or with spongiform or Glumyromyrmex is superficial and the result lamelliform appendages lamelliform appendages of convergence, and that the two genera do 10. Basal thud of first Basal third of first not share a close pliylogenetic relationship. gastral sternite with a gastral sternite without strong median longi- a crest (often with a tudinal crest median felt-like pad, sometimes bare) Relationship with Tatuidrh Brown & Kempf 11 Base of first gastral Base of fist gastral Discounting the forms mentioned above and tergite without a tergite with a transverse transverse crest of crest of lamellate or Pilotrochus, discussed below, the only other lamellate or spongiform spongiform tissue myrmicine genus which resembles Ishakidris tissue to any degree is Tutuidris Brown & Kempf (1967), which is known from El Salvador and In Ishakidris characters considered apo- Mexico. The resemblance is however verv morphic at this level of analysis are 1, 3, 4 and quickly analysed as superficial, as in Tutuidris 10; those considered apomorphic in Glamyro- the heavy mandibles are bidentate apically but rnyrmex are 2, 5, 6, 7, 9 and 11. Character 8 otherwise lack teeth, the palp formula is 1,2, remains as one whose plesiomorphic state is the eyes are situated at the posteriormost indeterminate at this level. apices of the scrobes, the propodeum is un- Chmyroinyrmex belongs to the smithi- armed and the middle and hind tibiae have strumiform dacetines (Brown, 1953; Bolton, pectinate spurs present. Apart from these 1983), a group of sixteen genera diagnosed telling characters the construction of the together as those members of the tribe Dace- petiole and postpetiole is radically different tini which have the eyes situated ventro- in Tutuidris, where the short thick sessile laterally on the head within or beneath the petiole which has a very large deep ventral scrobes, have the antennae 6- or 4-segmented process is followed by a postpetiole which is with the apical antennomere much the longest short, deep and very broad, and broadly of the funicular segments, have the palp attached to the gaster. Brown & Kempf formula 1,l and lack an apical fork of spini- (1 967) included Tatuidris in the tribe Agro- form teeth on the mandibles. Throughout all ecomynnecini, along with the fossil genera the smithistrumiform genera characters 1, 3, 4 Agroecomyrmex Wheeler and Eulithomyrmex and 10 of Ishakidris are universally absent. Of Carpenter. They noted the superficial simi- those given above as apoinorphies for Glamyro- larity of Tutuidris with Phulacromyrmex and myrrnex numbers 2, 5, 9 and 11 are also Glumyromyrmex but dismissed any suspicion present throughout the smithistrumiform of true phylogenetic relationship, concluding genera. (Character 6 is generally so but some that Tatuidris ‘is very strongly isolated among have the antennaereduced to only 4 segments; living ant genera, though clearly a myrmicine’. character 7 is variably developed.) Away from Glamyromyrmex also the habitus of the Relationship with Pilotrochus Brown smithistrumiform genera is markedly different from that of Ishakidris. In particular, of the Pilotrochus Brown (1977) is a very strange characters listed at the beginning of this sec- myrmicine ant known only from il single tion as corresponding between Ishakidris and worker specimen collected in a Berlese sample Glamyromyrmex, numbers 2, 5 and 6 are of forest litter and humus along the road to generally absent in other smit histrumiform AnosibC, 33 km south of Moramanga in east genera, and numbers 3, 4, 7 and I) constitute central Madagascar. The single species, P. Myrmicine antgenus Ishakidris 381

besmerus Brown, has I large teeth alternating higher level of classification and the three with denticles on the mandibular masticatory together may represent relicts of a once much margin, of which the apical tooth is smaller more common and widespread fauna. than the basals. The antennae are 8-segmented It would probably be safe to designate a and the funiculus ends in a strong 2-segmented tribal-group name to hold these three genera club. The frontal carinae are far apart and but, as the existing tribal-level classification expanded, and large deep scrobes are present within the Myrmicinae is in such a decrepit which have the eyes situated ventrolaterally. state, I can see no advantage to adding yet The propodeal spiracle is close to the margin another formal name to the confusion. Conse- of the declivity and tibia1 spurs are absent. quently I propose an informal genus-group, The petiole is curved-clavate and it and the the Phalacromyrmex-group, to hold these postpetiole in general are similar to Ishakidris. three genera until such time as a functional The apparently glandular mesopleural organ tribal classification of the Myrmicinae can be seen in Ishakidris is much more strikingly achieved. developed in Pilotrochus and is roughly Myrmicine ants belonging to the Phalacro- circular, though apparently not subtended myrmex-group are diagnosed by possessing by the open groove seen in Ishakidris. the following suite of characters in comhi- Despite these similarities there are a num- nation in the worker. ber of important characters in which Pilo- 1 Large to massive downcurved mandibles on trochus differs from both Ishakidris and which the teeth or denticles alternate in size from basal to preapical tooth. Phalacromyrmex. For instance, the mandibles 2 Ten or more teeth present (of all sizes) on are not strongly arched-downcurved as in masticatory margin of mandible, of which the the last two and the labrum is thickly lingui- apical tooth is not clearly the largest. form rather than bilobate. The frontal carinae 3 Mandibles lacking a basal lamella. are excavated immediately behind the narrow 4 Palp formula 3,2 or 2,2 (unknown in Pilo- lateral portions of the clypeusand do not flank tuochus). it laterally, so that in full-face view the antero- 5 Antennae 8-, 9- or 11-segmented, the flagellum lateral corners of the head are formed by the ending in a sharply defined club of 2 segments. lateral portions of the clypeus as is usual in 6 Ventral surface of head without a post-buccal myrmicines. The propodeum is unarmed, transverse groove or impression. lacking the lamellate spines characteristic of 7 Frontal carinae very far apart and expanded, forming the dorsal margins of deep and extensive Phalacromyrmex and Ishakidris. scrobes. Having considered the diagnostic characters 8 Clypeus broad and broadly inserted between the of Pilo trochus, Phalacromy rm ex and Is ha kidris, frontal carinae. and taking into account the shortage of material 9 Eyes situated ventrolaterally within or marginal in all three genera (including a complete lack to the scrobal area. of sexual and immature forms), I presently sus- 10 Alitrunk fused and the propodeal spiracle situ- ated close to the margin of the declivity (dis- pect that the similarities outweigh the counting any propodeal lamellae which may be differences sufficiently to imply a distant present). common origin for all three. In particular I 11 Petiole pedunculate anteriorly, the petiole and am impressed by the construction of the postpetiole lacking spongiform or lamelliform mandibles, antennae and pedicel segments, appendages. which are suspected of being synapomorphies 12 Middle and hind tibiae without spurs. rather than convergently acquired characters. By exclusion any myrmicine worker ant If Ishakidris and Phalacromyrmex are indeed which does not possess all of these characters related to Pilotrochus then the obvious corol- in combination is not a member of the Phala- lary is that Pilotrochus split from the parent cromyrmex-group. stock much earlier than Ishakidris and Phala- cromyrmex, which resemble each other much Key to genera of the Phalacromyrmexgroup more closely than either one resembles Pilo- (workers) trochus. summary then, whilst Pilotrochus In 1 Antennae with 8 segments. Frontal carinae not is not immediately related to Phalacromyrmex flanking lateral portions of clypeus. Labrum and Ishakidris, it may well be associated at a linguiform. (Madagascar) . . . Pilotrochus Brown 382 Barry Bolton

Antennae with 9 or 11 segments. Frontal carinae Brown, W.L., Jr (1953) Revisionary studies in the flanking lateral portions of clypeus. Labrum ant tribe Dacetini. The American Midland deeply bilobate ...... 2 Naturalist, 50, 1-1 31. Antennae with 11 segments. Occipital corners Brown, W.L., Jr (1977) An aberrant new genus of rounded. Base of first gastral sternite not carin- myrmicine ant from Madagascar. Psyche, 84, ate medially. Palp formula 3.2. (Brasil) 21 8-221. Phalacromyrrnex Kempf Brown, W.L., Jr & Kempf, W.W. (1967) Tatuidris, a remarkable new genus of Formicidae. Psyche, Antennae with 9 segments. Occipital corners 74, 183-190. acute. Base of first gastral sternite carinate Kempf, W.W. (1960) Phalacromyrmex. a new ant medially. Palp formula 2,2. (Sarawak) genus from southern Brasil. Revistu Brasiliera Ishakidris Bolton de Biologiu, 20, 89-92. References Bolton, B. (1983) The Afrotropical dacetine ants. Bulletin of the British Museum Natural History (Entomology),46, 267-416. Accepted 27 February 1984