Edward O. Wilson.
Ants of the Dominican amber (Hymenoptera: Formicidae). 1. Two new myrmicine genera and an aberrant Pheidole.
Psyche 92:1-10, 1985.

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ANTS OF THE DOMINICAN AMBER
(HYMENOPTERA: FORMIC-ID W.
1. TWO NEW MYRMICINE GENERA L~J*dL~
AN ABERRANT PHEIDOI å
BY EDWARD 0. WILSON
Museum of Comparative Zoology, Harvard I! ,iS i pi -.hd Cambridge, Massachusetts 02138, 1J.S A
Ants rival dipterans as the most abundant fossils in (tic s-~u:~ can Republic amber. Since they are also phylogeneticail ~u.:~gzr and relatively easily identified, these insects offer an c-.cchriir opportunity to study dispersal and evolution in a T;itiq $1 ?st Indian fauna.
The age of the Dominican amber has not ;et be. 11 tiei ir..i. but combined stratigraphic and foraminiteian adyss-s ^fit: ii; x r 2 suggest an origin at least as far back as the early Mia ?in , 1 . 1 i -,:
in Baroni Urbani and Saunders, 1982). 1 am inclini-ti 10 if , L' c minimal age (about 20 million years) or at most a lati. d':iG5 1.. origin, for the following reason. In a sample of 59o ainoo isi. .; containing an estimated 1,248 ants that I recemly excirninfd {W now deposited in the Museum of Comparative Zoblcg! ), i t-~.i.~-1 -?'? genera and well-defined subgenera, to which may br ai.J.L-'i r.oe other, Trachymyrmex, reported earlier by Baron] lli-bnns (i9tiui-:, Of these 37 taxa only three, or 8% are unknown ftocs. tho ii '1 g world fauna (see Table 1). The relative contempfiihixiii -å´ iir Dominican amber ants contrasts with that of the fidlu: di:.::r:. which is Eocene to early Oligocene in age (Larsson i97L) 5 ;2 X,
sesses 44% extinct genera; that is, 19 of the 43 geikia i~c\.~,lr~i u Wheeler (1914) are unknown among living ants. Ths. I,~,XILL~ 3, amber ants also differ to a similar degree frum thdse ci ill- h1i-s. sant, Colorado, shales, which are upper Oligocene in age an:i t * r.- tain 8 of 20, or 4096, extinct genera (Carpenter, 1930) Psiffte 92:l-10 11985). http//psychr enLclub.mgWMi2-OOl him)



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2 Psyche [VOI. 92
Table I, List of ant genera and well-defined subgenera known from the Domini- can amber. CBU: recorded by Baroni Urbani (1980a-d) and Baroni Urbani and Saunders (1982). CBU/EOW: recorded independently by both Baroni Urbani (1980a-d; and with Saunders.
1982) and E. 0. Wilson (hitherto unpublished). Generic names without accompanying initials represent determinations by the author and are recorded here for the first time. (*) unknown in modern faunas. Subfamily Ponerinae Oligomyrmex
Anochetus (CBU/ EOW)
* Osyidris, new genus
Cylindrumyrmex
Pararryptorerus (CBU / EOW)
Gnamptogeny.~ (CBU/ EOW) Pheidole
Hvpoponera
0donmmachu.s
Paraponera
P/at.rthyrea
Prionopelta
Truchyme.sopu.s
Subfamily Dorylinae
Neivamyrmex
Subfamily Pseudomyrmecinae
Pseudom~rmex (CBU/ EOW)
Subfamily Myrmicinae
A phaenogaster
Cremaiogaster (Acrocoelia)
New genus, near Rogeria
Smithi.struma
So1enop.si.s ( So1enopsi.s)
Solenopsis ( Diplorhoptrum)
Trachymyrniex (CBU)
[Zacryptorerus: see
Pararryp~~'erus]
Subfamily Dolichoderinae
Aziera
Do1ichoderu.s
Hvpoclinea
Iridoni~ex
[Leptomyrmex = Camponotus'?,
CBU/ EOW]
Monads (CBUI EOW)
Cremawgaster (Orthocrema) Tapinoma
*Ilemoni}*rmex, new genus Subfamily Formicinae Leptothorax ( Macromisrha) Camponoius
Lepiothorax ( Nesomyrmex) Paratrechina
Octostruma Prenolepis
The purpose of this first article of a planned series on the Domini- can fauna is to describe the three most distinctive new species encountered in any collection known to me: two new myrmicine genera (Ilemomyrmex, Oxyidris) and a remarkable pheidoline which 1 have provisionally placed in the genus Pheidole. Ilemomyrmex, new genus
Diagnosis (worker). Small, eyeless myrmicine possessing the fol- lowing distinctive combination of features: large, flaring frontal lobes that are raised well above the antennal insertions and cover most of the clypeus in full-face view; shallow antennal scrobes with



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19851 Wilson - Dominican amber ants. 1 3 posterior margins curving laterally to embrace the ends of the scapes; paired clypeal carinae close together and projecting beyond the remainder of the anterior clypeal margin to form a short concav- ity between them; narrow, 3- or 4-toothed mandibles (apical region indistinct in the single specimen available); and 12-segmented antennae with 3-jointed clubs.
Queen (tentative association):
Overall similar to worker, except
that frontal lobes extend only part way over clypeus; mandibles are 5-toothed; and eyes and ocelli are well developed. (From Gr. eiiema, envelope; and Gr. myrmex, ant).
Type species: Ilemomyrmex caecaus.
Ilemomyrmex caecus, new species
(Figs. 1, 2)
Diagnosis {~wrker).
Distinguished from all other known ant
species by the combination of traits cited above for Ilemomyrmex. In addition, possessing a robust alitrunk with thick, triangular propodeal spines; and short, thick petiole and postpetiole, the latter with an acute, forward-projecting ventral spine. Hdotype worker. Head Width 0.51 mm, Head Length 0.58 mm, Scape Length 0.44 mm. Head coarsely rugoreticulate and completely opaque, the rugae near the rims of the antennal scrobes parallel to one another and following the contours of the rims. Entire alitrunk and waist similarly rugoreticulate and opaque, but the gaster is nearly smooth and is feebly shining to subopaque. Color (which may not have remained true in the fossil state) dark reddish brown.
Queen (tentative association). Winged. Differing from worker as described in generic diagnosis. Head Width (across and including eyes) 0.52 mm, Head Length 0.54 mm, Eye Length 0.16 mm. Based on a single (holotype) worker and one alate queen in separ- ate pieces of Dominican amber; no further locality data. Both spec- imens have been deposited in the Museum of Comparative Zoology. Ilemomyrmex resembles the Old World, principally African gen- era Calvptomyrmex and Dicroaspis in antennal form and the pecul- iar shape of the frontal lobes. However, it differs from them in the following important respects: its mandibles are narrower, with fewer teeth (5 or more in Calvptomj~rmex and Dicroaspis); its antennal scrobe is much shallower; its subpostpetiolar process is better devel- oped; its head is narrower and overall less modified from the primi-



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Psyche
[Vol. 92
Fig. 1 . llemom,~~r~?ie.x cuecux. Holotype worker: A, frontal view of head; B. oblique rear view of head; C. side view of body. Fig. 2. flenioniynvex cawus. Frontal view of head of queen provisionally placed in this species.




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IYÌö~ wuson - uorninican amber ants. I 5 tive myrmicine shape; and its hairs are thinner and less uniform and regularly distributed (furthermore, in Ca/vptom.~*rmex and Dicro- aspis the hairs are blunt-tipped or, in the case of most species, spatulate or scale-shaped). In addition, Dicroaspis has 11- segmented antennae. 1 am inclined to regard the resemblance in frontal lobe shape between Hemomyrmex and the two African gen- era as having arisen by convergent evolution. Oxyidris, new genus
Diagnosis (worker).
A very small myrmicine with closest overall resemblance to the South American genus Oxyepoecus, particularly in the general form of the antenna and waist; but differing in its lack of eyes, its 12-segmented antennae (1 1 in Oxyepoecus), in its 3 (pos- sibly 4) mandibular teeth (4-5 in Oxyepoecus), and in its unarmed propodeum (angular or spinous in Oxyepoecus). (From Gr. oxys, sharp, acute; and Gr. idris, wise one; also to note resemblance to Oxyepoecus).
Type species: Oxyidris antWana.
Oxyidris antillana, new species
(Fig. 3)
Diagnosis (worker). Distinguished from all known ant species by the combination of traits just described for Oxyidris. Holotype worker.
Head Width 0.36 mm, Head Length 0.45 mm, Scape Length 0.30 mm. Antenna 12-segmented with 3-jointed club. Head densely and evenly rugulo-punctate (rugulae with longitudinal orientation) and opaque. Alitrunk and waist densely and uniformly punctate, and opaque. Gaster shagreened, subopaque. Color (which may be altered in the fossil state) light reddish brown. Dominican Republic: Palo Quemado Mine, Santiago Province. Paratvpe workers. Six additional workers, one each in 6 amber pieces from Palo Quemado Mine.
Holotype and paratypes deposited in the Museum of Compara- tive Zoology.
Pheidole tethepa, new species
(Figs. 4, 5)
Diagnosis (minor worker). An unusual pheidoline tentatively placed in Pheidole, differing from all known species of that genus by



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Psyche
Fig. 3.
0.yriilris uti~illutiu. Holotype worker: A, frontal view of head: B, side view of body.
the bulging, more-than-hemispherical eyes, and proportionately very large mandibles. Pronotum armed with two well-developed spines, a trait shared with members of the Old World P. quadrispina group but not with any known living New World Pheidole species. (Gr. tethepa, amazed; referring to the eyes). Holotvpe minor worker. Head Width exclusive of eyes 0.76 mm, Pronotal Width 0.43 mm. Eyes with approximately 30 ommatidia. Head sparsely rugose to rugoreticulate with predominantly longi- tudinal orientation. Pronotum with several transverse rugae. Rest of dorsal surface of alitrunk evenly shagreened and subopaque. Paratype minor workers.
Two individuals poorly preserved but
clearly sharing the diagnostic traits of the holotype. Holotype and paratypes in a single amber piece from La Toca Mine, Dominican Republic.
Are Ilemomyrmex and Oxyidris really extinct? If so, they are extreme exceptions in the generic ranks of the Dominican amber ants. It may be significant that both are small, eyeless, and possess narrow, sharp-toothed mandibles. In addition, Ilemomyrrnex is dis- tinguished by expanded frontal lobes and scrobes that together can mostly cover the antennae. In the living fauna these traits are charac- teristic of cryptobiotic, often scarce myrmicine ants that are among the last to be collected and recognized. Examples of such living genera that have been recently discovered or at least recognized as



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19851 wuson - uomimcan arneer ants. I
Fig. 4.
Pht~i(1ole u'//~t~pu. Holotype worker: A, dorsal view of head and body; B, frontal view of head and pronoturn.
Fig. 5.
Phdilole reihepa. Paratype worker from holotype amber piece, showing different view of body and head.




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hiyber taxa in the New World tropics are Creightonidris (1949), D~r~sidi is { 1948). Phdarrumyex ( 1960). Proiuiuridris ( !98O), arid 7'a1111dri.r (1967). Hence it is entirely possible that contempo- i aneous species of ilemomyrmex and O.rjaidrh may yet be disco- vered. although not necessarily in the West indies. Plwitiut~ i~thepa has been placed in the genus Pheidole as a pro- visional measure. It may well represent a phyletic line sufficiently <iii~erefcni from other members of the tribe Pheidolini to justify getisric 1 ank The exophthalmic eyes and proportionately large mat ~dibles an; unique within Pheidole on a worldwide basis, while tlie pronotal spines were almost certainly derived independently from the Old W orid P. quadrispinu group. More material is clearly rieeded to resolve the matter. In particular, the demonstration of a large- headed major caste (if one exists) would give added reason to retzin /cikpa in Pheidole,
I am grateful to Cesare Baroni Urbani, Barry Bolton, and Wil- liam L. Brown for their advice on the three new species described heie. The research was supported by National Science Foundation giarit no. BSR 81-19350.
~^I,H\I 1'11tn~. C
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f-ir-it description ol lcissil gardening anis (Amber Collcclion Stuttgart and Natural Hisinry Museum Basel: Hymenoptera. Formicidac. 1: AltmiL Stimprtcr Bcitr, Nalurk . B(Gcol. Paliiftntol.). 54: 1 13. 'Wt- Aiii~iintfi ~iovi n sp.. the first fossi! Odontomachiti an! (Amber Col- kctkin Sluiigart: Hymcnqticra. Forrnicidac. II: Odontomachiti). Stuw gitrirt Bcii~. Nsiturk . B (tied. Paiklontol.). SS: 1 ft. i Wk
The !irsi low! species of the Australian ant genus t.rptimivrtm~x in amhrr I'ioin the Dominican Republic (Amber Colicction Stuttgnrl: Hynt~inptcra. Formicidac. Ill: Lcptornyrmicini). Sliittwrter Beilr. Nalurk . B (Gct~l. Paliontol.). 62: 1 10. ! Wfd
'I he iini p-1~5 Giwwp~vnp in Dominican amber (Amber Collection 'hungiiri; Hvwnoptera. Formicidae. IV: Ectaiommini). Stuttprler Briir Ktilurk.. B (Geol PaBontol.). 67: 1 10. H iiv!~ I'IIIIA~!, C A^T> J. t) SAI vni u*i. IW2 The luumi at the Dominican Republic amber: The present status nr ki'~iwktIgc. Trans, 9th Caribbean Gcol. Conference. Santo Domingo, Dcm Htyi., 1980 (1982). I- 213 22.1.




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CAR~'~-.N'?%. T'. M.
1930. The fossil ants of North America. Bull. Mus. Comp. Zool. Harvard, 70: 1-66. !I pi.
LARSSON. S. Go
i 9%. Emosi~otwgwph (Klampenborg. Denmark), 1: I 192. W?ii:i:~.!;~. W. M.
5934. The ants of the Baltic amber. Schrift. physikal.-Okon. Ges. Kihigsberg. 55: M42.




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