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2(1), 1993 pp. 117-168 

Systematic studies on Pseudomyrmex acacia-ants 
(Hymenoptera: Formicidae: Pseudomyrmecinae) 


Department of Entomology, University of California, Davis, CA 956 1 6 

Abstract. The obligate acacia-ants ( Pseudomyrmex ferrugineus group) are well known as defensive inhabitants 
of swollen-thorn acacias in the northern Neotropics. A taxonomic revision of these ants leads to the recognition of 
ten species: P. ferrugineus (F. Smith), P. flavicornis (F. Smith), P. janzeni, sp. nov., P. mixtecus, sp. nov., P. 
nigrocinctus (Emery), P. particeps, sp. nov., P. peperi (Forel), P. satanicus (Wheeler), P. spinicola (Emery), and 
P. veneficus (Wheeler). The following new synonymy is proposed: P. nigrocinctus = P. alfari (Forel) = P. bicinctus 
(Santschi) = P. peltatus (Menozzi); P. spinicola = P. atrox (Forel) = P. gaigei (Forel) = P. infernalis (Wheeler) = 
P. scelerosus (Wheeler). Diagnostic descriptions and taxonomic comments are also provided for ten other unrelated 
species of Pseudomyrmex which have become secondarily associated with swollen-thorn acacias either as obligate 
and, in at least one case, parasitic occupants (P. nigropilosus (Emery), P. simulans Kempf and P. subtilissimus 
(Emery); P. reconditus, sp. nov., may also belong in this category) or as facultative inhabitants ( P. boopis (Roger), 
P. gracilis (Fabricius), P. hesperius, sp. nov., P. ita (Forel), stat. nov., P. kuenckeli (Emery) and P. opaciceps, sp. 
nov.). A cladistic analysis of the P. ferrugineus group yields the following result which appears to be fairly robust 
insofar as there is congruence among the trees derived from worker-, queen-, and male-based character sets: 
((nigrocinctus + particeps) + (peperi + ((satanicus + spinicola) + ferrugineus complex))). The "ferrugineus 
complex" comprises five species whose phylogenetic relationships are not fully clarified. The composite data set 
(47 characters from all three castes) supports the following partial resolution: (ferrugineus + janzeni + (flavicornis 
+ (mixtecus + veneficus))). The cladogram of the P. ferrugineus group indicates that speciation in the group has 
occurred primarily as a consequence of geographical isolation, and that the ants and their host acacias have 
experienced diffuse coevolution rather than strict cospeciation. 

INTRODUCTION men ts have appeared in the ecological literature. In 

this paper I present a taxonomic revision of the 

Pseudomyrmex ferrugineus (F. Smith) and re- obligate acacia-ants (Pseudomyrmex ferrugineus 
lated species of ants form a well-defined mono- group) and an assessment of their phylogenetic 
phyletic group, the members of which nest exclu- relationships. I also attempt to clarify the identities 
sively in the hollow, swollen thorns of several New of other, unrelated species of Pseudomyrmex which 
World Acacia species. Because of their aggressive have become secondarily associated with swollen- 
behavior and predictable occurrence on the acacias, thorn acacias. 

these ants have received considerable attention The earlier taxonomic literature on acacia-ants 

from tropical biologists (Belt 1874; Safford 1922; is scattered in more than a dozen papers containing 

Skwarral934a,1934b; Wheeler 1942; Janzen 1966, descriptions of various species, subspecies, and 

1973). The landmark studies of Janzen (1966, "varieties". Two of the more comprehensive treat- 

1967b) provided strong experimental evidence of ments are those of Emery (1890) and Wheeler 

the mutualistic nature of the Pseudomyrmex/Aca- (1942). In presenting the results of his ecological 

cia association, and the relationship between the studies Janzen (1966, 1967b, 1973) summarized 

two organisms is often cited in discussions of his understanding of acacia-ant taxonomy. Ward 

coevolved mutualisms (e.g. Gilbert 1983; Beattie (1989) provided a brief diagnosis of the P. 

1985; Futuyma 1986). At the same time, the ferrugineus group, together with taxonomic and 

systematics of the acacia-ants has been neglected, nomenclatural notes on the commoner species, 
with the result that misidentifications and misstate- 




Material for the present study was examined in 

the following collections: 

AMNH American Museum of Natural History, New 
York, NY, USA 

ANSP Academy of Natural Sciences, Philadel- 
phia, PA, USA 

BMNH The Natural History Museum, London, 

CASC California Academy of Sciences, SanFran- 
cisco, CA, USA 

CHAH C.H.A. Hespenheide Collection, Univer- 
sity of California at Los Angeles, C A, USA 

CISC California Insect Survey, University of 
California at Berkeley, CA, USA 

CUIC Cornell University Insect Collection, 
Ithaca, NY, USA 

EBCC Estacion de Biologia Chamela, Jalisco, 

FFIC Fernando Fernandez Collection, Santa Fe 
de Bogota, Colombia 

GBFM Graham B. Fairchild Museo de 
Invertebrados, Universidad de Panama, 

GCWCG.C. & J. Wheeler Collection, Silver 
Springs, FL, USA 

INBC Institute Nacional de Biodiversidad (col- 
lections previously held in MNCR: Museo 
Nacional de Costa Rica), San Jose, Costa 

INKS Illinois Natural History Survey Insect Col- 
lection, Champaign, IL, USA 

JTLC J.T. Longino Collection, Evergreen State 
College, Olympia, WA, USA 

KSUC Kansas State University Insect Collection, 
Manhattan, KS, USA 

LACM Natural History Museum of Los Angeles 
County, Los Angeles, CA, USA 

MCSN Museo Civico di Storia Naturale, Genoa, 

MCZC Museum of Comparative Zoology, Harvard 
University, Cambridge, MA, USA 

MHNG Museum d'Histoire Naturelle, Geneva, 

MNHN Museum National d'Histoire Naturelle, 

Paris, France 

MZSP Museo de Zoologia da Universidade de 
Sao Paulo, Brazil 

NHMB Naturhistorisches Museum, Basel, Swit- 

NHMV Naturhistorisches Museum, Vienna, Aus- 

PSWC P.S. Ward Collection, University of Cali- 
fornia at Davis, CA, USA 

SEMC Snow Entomological Museum, University 
of Kansas, Lawrence, KS, USA 

UCDC Bohart Museum of Entomology, Univer- 
sity of California at Davis, CA, USA 

UCRC UCR Entomological Collection, Univer- 
sity of California at Riverside, CA, USA 

USNM National Museum of Natural History, 
Washington, DC, USA 

WPMC W.P. MacKay Collection, El Paso, TX, 

ZMHB Zoologisches Museum, Museum fur 
Naturkunde der Humboldt-Universitat, 
Berlin, Germany 

ZMUC Zoologisk Museum, University of 
Copenhagen, Denmark 

ZMUH Zoologisches Institut und Zoologisches 
Museum der Universitat Hamburg, Ger- 

ZSMC Zoologische Staatssammlung, Munich, 

Special mention should be made of the very 
large and important series of Pseudomyrmex col- 
lected by D.H. Janzen from 1963 to 1974 and now 
housed in the Natural History Museum of Los 
Angeles County (LACM). The Janzen material 
includes a large number of pinned specimens (usu- 
ally glued to the side of the pin rather than point- 
mounted) and an extensive alcohol collection (partly 
overlapping with the pinned series but including 
additional accessions). Janzen's field notes per- 
taining to the collection of these ants have also been 
deposited in LACM. Obligate acacia-ants (P. 
ferruginem group) constitute the bulk of the col- 
lected material. They occur as long nest series from 
throughout Central America, with very useful queen- 
male-worker associations, making this material of 
inestimable value to the current revision. 

VOLUME 2, NUMBER 1, 1993 


When the Janzen collection was received at 
LACM in 1984 most specimens had only code 
numbers associated with them among the pinned 
specimens a single individual per nest series typi- 
cally contained a code number, with the remaining 
specimens being unlabelled and in some instances 
difficulties arose in retrieving full data for coded 
specimens from Janzen' s field notes. In other cases 
the field notes contradicted the apparent identity or 
composition of a nest series. This latter problem 
applied mainly to pinned specimens; the alcohol 
material appeared to be reliably labelled or coded, 
i.e. the contents of the vials agreed with the field 
notes. Thanks to the efforts of Roy Snelling and 
Jack Longino, who incorporated the Janzen collec- 
tion into the LACM, many of these discrepancies or 
uncertainties were resolved, but there remains a 
residue of "problem material" for which collection 
data are lacking or ambiguous. Among the pinned 
specimens this comprises twelve drawers in the 
LACM collection which have been specifically set 
aside from the main collection. None of this prob- 
lematical material has been cited in the present 
study, but I have examined it and determined that 
no additional species are represented there. Al- 
though omission of this material means the poten- 
tial loss of some locality data, I have examined the 
entire alcohol collection and point-mounted repre- 
sentative samples so that geographic coverage re- 
mains extensive. The main pinned series of LACM 
acacia-ants, i.e. that for which accurate data labels 
are available, comprises 30 drawers and approxi- 
mately 20,000 specimens, the great majority of 
which were collected by Janzen. 


All measurements were made under a Wild 
microscope at SOX power, using an orthogonal pair 
of Nikon micrometers wired to a digital readout. 
Measurement conventions follow those described 
in Ward (1985, 1989). Note that a full-face or 
dorsal view of the head involves positioning the 
posterior margin and the anterolateral margins 
(above the mandibular insertions) so that they lie in 
the same plane of view. 

The following measurements and indices are 

cited in this study (the first six measurements are 

taken with the head in a full-face, dorsal view): 

HW Head width: maximum width of head, in- 
cluding the eyes. 

VW Vertex width: width of the posterior portion 
of the head (vertex), measured along a line 
drawn through the lateral ocelli. 

HL Head length: midline length of head proper, 
from the anterior clypeal margin to the mid- 
point of a line drawn across the "occipital" 
(i.e. posterior) margin. 

EL Eye length: length of compound eye; note 
that this is measured with the head in full 
face, dorsal view, unlike EW(below). 

OD Ocellar distance: distance from the middle of 
the median ocellus to the midpoint of a line 
drawn between the lateral ocelli. 

OOD Oculo-ocellar distance: distance from the 
middle of the median ocellus to the midpoint 
of a line drawn across the posterior margins 
of the compound eyes (this distance is nega- 
tive in value if the posterior margin of the 
compound eye exceeds the median ocellus). 

MFC Minimum frontal carinal distance: minimum 
distance between the frontal carinae, poste- 
rior to their fusion with, or approximation to, 
the antennal sclerites. 

ASD Antennal sclerite distance: maximum dis- 
tance between the lateral margins of the me- 
dian lobes of the antennal sclerites, measured 
in full-face, dorsal view of the head. 

ASO Antennal sclerite distance, outer margins: 
maximum distance between the outer, lateral 
margins of the antennal sclerites. 

CLW Width of median clypeal lobe, measured 
between the anterolateral angles (in 
Pseudomyrmex satanicus and P. spinicola 
only; see Figs. 10, 11). 

MD4, MD5, MD8, MD9 A series of mandibular 
measurements (see Ward 1989, figure 2). 
MD4: distance along the basal margin of the 
mandible from the base to the mesial basal 
tooth; MD5 : length of the basal margin ; MD8 : 
distance along the masticatory margin from 
the apex to the fourth tooth, counting from 
the apex; MD9: length of the masticatory 



EW Eye width: maximum width of compound 
eye, measured along its short axis in an 
oblique dorsolateral view of the head. 

SL Scape length: length of the first antennal 
segment, excluding the radicle. 

LF1 Length of first funicular segment: maximum 
measurable length of the first funicular seg- 
ment (pedicel), including its basal articula- 
tion in workers and queens but excluding the 
basal articulation in males (where it is usu- 
ally hidden). 

LF2 Length of second funicular segment: maxi- 
mum measurable length of the second 
funicular segment. 

LF3 Length of third funicular segment: maxi- 
mum measurable length of the third funicular 

WF2 Width of second funicular segment, 

FL Profemur length: length of the profemur, 
measured along its long axis in posterior 
view (see Ward 1985, figure 3). 

FW Profemur width : maximum measurable width 
of the profemur, measured from the same 
view as FL, at right angles to the line of 
measurement of FL. 

DPL Diagonal length of the propodeum: length of 
the propodeum, measured in lateral view 
along a diagonal line drawn from the 
"metapleural" lobe to the metanotal groove 
(see Ward 1985, figure 2). 

BF Length of the basal (=dorsal) face of the 
propodeum, measured in lateral view from 
the metanotal groove to the point on the 
surface of the propodeum which is maxi- 
mally distant from the diagonal propodeal 

DF Length of the declivitous face of the 
propodeum, measured in lateral view from 
the "metapleural" lobe to the point on the 
surface of the propodeum which is maxi- 
mally distant from the diagonal propodeal 

MP Depth of metanotal groove ("mesopropodeal 
impression"), measured in lateral view from 
the bottom of the metanotal groove to a line 
drawn across the dorsal surface of the 
mesonotum and propodeum. 

PL Petiole length: length of the petiole, mea- 
sured in lateral view from the lateral flanges 
of the anterior peduncle to the posterior mar- 
gin of the petiole (see Ward 1985, figure 4). 

PND Petiolar node distance: distance from the 
lateral flanges of the anterior petiolar pe- 
duncle to the maximum height of the node, 
measured from the same view as PL and 
along the same line of measurement (see 
Ward 1985, figure 4). 

PH Petiole height: maximum height of the peti- 
ole, measured in lateral view at right angles 
to PL, but excluding the anteroventral pro- 

PPL Postpetiole length: length of the postpetiole, 
measured in lateral view, from the anterior 
peduncle (of the postpetiole) to the point of 
contact with the fourth abdominal tergum, 
excluding the pretergite (see Ward 1985, 
figure 4). 

DPW Dorsal petiolar width: maximum width of the 
petiole, measured in dorsal view. 

MPWMinimum petiolar width: minimum width of 
the petiole,measured in dorsal view, anterior 
to DPW. 

PPW Dorsal postpetiolar width: maximum width 
of the postpetiole, measure in dorsal view. 

LHT Length of metatibia: maximum measurable 
length of metatibia, excluding the proximal 
part of the articulation which is received into 
the distal end of the metafemur (see Ward 
1989, figure 5). 

CI Cephalic index: HW/HL 

OI Ocular index: EW/EL 

REL Relative eye length: EL/HL 

REL2Relative eye length, using HW: EL/HW 

OOI Oculo-ocellar index: OOD/OD 

VI Vertex width index: VW/HW 

FCI Frontal carinal index: MFC/HW 

FCI2 Frontal carinal index, using ASD: MFC/ASD 

ASI Antennal sclerite index: ASD/ASO 

SI Scape index: SL/HW 

SI2 Scape index, using EL: SL/EL 

FLI Funicular length index: (LF2 + LF3)/WF2 

FI Profemur index: FW/FL 

PDI Propodeal index: BF/DF 

MPI Metanotal index: MP/HW 

NI Petiole node index: PND/PL 

VOLUME 2, NUMBER 1, 1993 


PLI Petiole length index: PH/PL 

PLI2 Petiole length index, using PPL: PPL/PL 

PWI Petiole width index: DPW/PL 

PWI2 Petiole width index, using PPW: DPW/PPW 

PWI3 Petiole width index, using MPW: MPW/ 

PWI4 Petiole width index, using LHT: DPW/ 

PPWI Postpetiole width index: PPW/PPL 

Other Conventions 

Other terminology follows the usage in Ward 
(1989). Note that descriptions of surface sculpture 
and integument reflectance apply to observations 
made under soft light, with an opaque (Mylar) filter 
placed between the specimens and source of illumi- 
nation. Palp formula refers to the number of max- 
illary palp segments followed by the number of 
labial palp segments; 5p4,3 indicates a condition 
intermediate between 5,3 and 4,3, i.e. partial fusion 
of the fourth and fifth maxillary palp segments. 

Listing of synonymy under each species is re- 
stricted to citation of the original descriptions (with 
full reference given for all previously proposed 
junior synonyms) and new nomenclatural combi- 
nations. For ecologists a more useful summary of 
name usage is offered in Table 1 , which indicates 
the correspondences between the names appearing 
in the biological literature on acacia-ants and the 
currently valid scientific names. The reader will 
appreciate that there has been considerable 
misidentification of these ants. 

In the lists of material examined of each species, 
I have cited only locality and collector ("c.u." 
signifies collector unknown), with the source col- 
lections listed together at the beginning. Additional 
locality information is sometimes provided in square 
brackets, to facilitate location of the collecting site. 
Considerable effort was expended to determine the 
coordinates (latitude and longitude) of each collect- 
ing site, and this was then used in conjunction with 
the public domain software program Versamap 
(version 1.20) to plot the distributions of each 
species (Figs. 67-72). 

Cladistic Analysis 

A set of 47 characters, representing the most 
discrete or quantifiable differences among species 
or groups of species in the P. ferrugineus group, 
was used for phylogenetic analysis. Twenty of 
these characters were worker-based (11 of these 
manifested the same conditions in queens), 8 were 
queen-based, and 19 were taken from male mor- 
phology, primarily male genitalia. The characters 
and character states are as follows: 

1. Worker, median clypeal lobe (0) laterally 
rounded or subangulate, ( 1 ) laterally with sharp 
angles or teeth (Figs. 10, 11). 

2. Worker and queen, frontal carinae (0) rela- 
tively well separated, median lobes of anten- 
nalsclerites less exposed (Figs. 12-19, 32), (1) 
closely adjacent and median lobes of antennal 
sclerites more exposed (Figs. 10, 11, 32). 

3. Worker and queen, palp formula (0) 5,3, (1) 

4. Worker, head (0) broader, relative to HL, DPL 
and PL, (1) narrower; see regressions of HL, 
DPL and PL on HW (Figs. 36-38). 

5. Worker, scape (0) short, relative to HL, (1) 
longer; regression of SL on HL lying above 
that of other species. 

6. Worker, conspicuous pit-like impression on 
midline of head (0) absent, (1) present. 

7 . Worker, petiole (0) short relative to postpetiole, 
PLI2 0.77, (1) longer relative to postpetiole, 
PLI2 < 0.77. 

8. Worker and queen, petiole (0) without a well 
differentiated anterior peduncle, i.e. weakly 
constricted in dorsal view and with little or no 
inflection of the anterior face of the petiole in 
lateral profile (Figs. 22, 23), (1) with a well 
differentiated peduncle (Figs. 20, 21, 24-29). 

9. Worker and queen, petiole, dorsal view, 
angulate posterolateral corners (0) absent, (1) 
moderately developed, preceded by convex or 
sinuate sides (e.g. Figs, 20, 27), (2) very promi- 
nent, preceded by more or less straight sides 
(Fig. 24). 

10. Worker and queen, petiole (0) shorter and 
higher, worker PLI 0.71, queen PLI 0.64, 



(1) more slender, worker PLI < 0.72, queen 
PLI < 0.64. 

11. Worker, DPW relative to HW (0) narrow, (1) 
broader, (2) very broad; see regression of 
DPW on HW (Fig. 41). 

12. Worker, plot of PWI3 by HW lying in (0) 
upper left ( 1 ) lower right (2) lower left region, 
of Fig. 39. 

1 3 . Worker and queen, plot of PWI4 by HW lying 
in (0) center and lower right (1) upper left (3) 
lower left region, of Fig. 40. 

14. Worker, postpetiole (0) broad, PPWI > 1.30, 
(1) narrow, PPWI 1.00-1.30. 

1 5 . Worker, metatibia (0) short, relative to HL, ( 1 ) 
relatively long; see regression of LHT on HL 
(Fig. 30). 

16. Worker and queen, head sculpture (0) densely 
punctulate, subopaque to sublucid, at least on 
upper third of head, (1) densely punctulate, 
opaque, (3) punctulate-coriarious, opaque 

17. Worker and queen, propodeum, posterolat- 
eral portions (0) sublucid, without overlying 
rugulo-punctate sculpture, (1) supopaque to 
opaque, with rugulo-punctate sculpture. 

18. Worker and queen, petiolar node (0) lacking 
conspicuous suberect pubescence, (1) with 
such pubescence. 

19. Worker and queen, standing pilosity on exter- 
nal faces of tibiae (0) present, (1) absent. 

20. Worker and queen, head and gaster (0) yel- 
low- to orange-brown, (1) reddish-brown to 
medium or dark brown, (2) very dark brown to 
black (excluding mandibles, clypeus and 

21. Queen, size (0) small, HW 0.85, (1) medium 
to large, HW 0.85. 

22. Queen, head shape, for a given LHT (0) elon- 
gate, (1) less elongate, (2) broad (see Fig. 52). 

23. Queen, petiole (0) short, relative to HW, PL/ 
HW < 0.7 1 , ( 1 ) longer, PL/HW 0.71. 

24. Queen, petiole (0) short, relative to HL, (1) 
longer: see regression of PL on HL (Fig.46). 

25. Queen, regression of PH on HW lying in (0) 
upper (1) middle (2) lower region, in Fig. 47. 

26. Queen, petiole, dorsal view (0) narrow, rela- 
tive to HL, (2) broader; regression of DPW on 

HL lying above that of other species. 

27. Queen, metatibia (0) short, relative to HL, 
LHT/HL < 0.62, (1) longer, LHT/HL > 0.66. 

28. Queen, metatibia (0) short, relative to HW, (1) 
longer; see regression of LHT on HW (Fig. 

29. Male, head (0) narrower, CI 0.82-0.94 and 
HW < 0.96, (1) broader, CI 0.94 and/or HW 

0.96 (regression of HL on HW lying below 
that of other species). 

30. Male, scape index (SI) (0) 0.22-0.30, (1) 0.29- 
0.35, and regression of SL on HW lying above 
that of other species. 

3 1 . Male, scape length, relative to EL and HL (0) 
long, SI2 0.43-0.56, SL/HL 0.22, (1) 
shorter, SI2 0.33-0.43, SL/HL 0.21 (and 
regression of SL on HL lying below that of 
other species). 

32. Male, compound eye length, relative to HW 
(0) long, REL2 0.56-0.63, (1) shorter, REL2 
0.49-0.58, and regression of EL on HW lying 
below that of other species. 

33. Male, petiole (0) less slender, PLI > 0.45, (1) 
more slender, PLI < 0.50, and regressions of 
PH and DPW on LHT lying below those of 
other species. 

34. Male, sternite IX, posterior margin (0) con- 
vex, (1) with a moderate concavity, less than 
semicircular (Fig. 54), (2) with a deep, semi- 
circular concavity (Fig. 55). 

35. Male, paramere, lateral view, posterodorsal 
extremity (0) rounded, (1) angulate or ex- 

36. Male, paramere, lateral view, posterodorsal 
extremity (0) not projecting caudad, (1) pro- 
jecting caudad, as in Figs. 56, 57. 

37. Male, paramere, lateral view, posterodorsal 
extremity (0) not developed as a lobe-like 
protrusion, whose mesial face is a saucer-like 
concavity, (1) so developed (Figs. 61-66). 

38. Male, paramere, lateral view, posterodorsal 
extremity (0) well separated from mesiodorsal 
lobe, (1) close to mesiodorsal lobe, enclosing 
a narrow space between it and the lobe (Figs. 
58, 61-66). 

39. Male, paramere, digitiform mesiodorsal lobe 
(0) absent, ( 1 ) present, slender, directed poste- 

VOLUME 2, NUMBER 1, 1993 


riorly or posterodorsally (Figs. 56-60, 63-65), 
(2) present, stubby, directed more or less dor- 
sally (Figs. 61, 62). 

40. Male, paramere, mesial face of posterodorsal 
extremity (0) simple in form, not expanded 
mesially, (1) expanded mesially, partly ob- 
scuring the mesial dorsoventral ridge in poste- 
rior view. 

41. Male, aedeagus, posterior margin (0) entire, 
not medially pointed, (1) toothed, and medi- 
ally pointed. 

42. Male, aedeagus, posterior margin (0) bent 
posterolaterally, (1) bent anterolaterally, (2) 
bent anterolaterally but with the medial point 
redirected posteriorly. 

43. Male, aedeagus, laterally bent portion of pos- 
terior margin (0) continuous with the margin 
of the posterodorsal extremity,(l) discontinu- 
ous with margin of posterodorsal extremity 
(elevated laterally), the two connected by a 
gradual slope, (2) discontinuous with margin 
of posterodorsal extremity, elevated laterally, 
and separated by a trenchant rise (posterior 
view) from the posterodorsal extremity. 

44. Male, aedeagus, plate-like expansion of 
posterodorsal extremity (0) absent, (1) mod- 
erately developed, (2) strongly developed. 

45. Male, aedeagus, external face (0) without a 
large, central elevated area, (1) with a central 
elevated area, delimited posteroventrally by a 

weak ridge or carina, (2) with a central el- 
evated area, delimited posteroventrally by a 
strong lamellate carina. 

46. Male, aedeagus, external face, afore-men- 
tioned carina (if present) (0) well separated 
from the toothed posterior margin, ( 1 ) running 
close to and more or less parallel with the 
toothed posterior margin but separated by a 
deep groove, (2) converging posterodorsally 
with the toothed posterior margin. 

47. Male, aedeagus, postero ventral extremity (0) 
broadly rounded, (1) subangulate, (2) angulate 
with a tooth-like protrusion. 

The data set was analyzed using Farris' Hennig86 
program. Characters 12, 13 and 16 were considered 
unordered. As an outgroup I chose Pseudomyrmex 
fervidus (F. Smith), a Central American species 
which shares a number of (mostly worker) features 
in common with the P.ferrugineus group: 5,3 palp 
formula, similar mandibular dentition, well devel- 
oped metanotal groove, abundant pilosity on 
mesosoma dorsum, relatively small eyes, and a 
similar habitus with respect to size and color. In a 
few instances the outgroup species spanned the 
phenotypic gap between two discrete states in the 
ingroup; it was then coded as unknown for that 
character. In addition to seeking the most parsimo- 
nious tree for the entire data set (rooted with the 
outgroup), I also compared the cladograms based 
on three subsets, derived from the worker, queen, 
and male characters sets, respectively. For this 
second analysis the queen character set included 
the eight characters assessed only in queens (2 1 -28) 
plus those manifested identically in workers and 
queens (2, 3, 8-10, 13, 16-20), for a total of 19 




Figs. 1-9. Pseudomyrmex workers, lateral view of mesonotum, propodeum and petiole, with pilosity shown in 
outline; Figs. 4 and 5 include a frontal view of worker head. 1 , P. boopis (Costa Rica); 2, P. ita (Costa Rica); 3, P. 
kuenckeli (Costa Rica); 4, P. hesperius (Mexico, paratype); 5, P. opaciceps (Guatemala, paratype); 6, P. gracilis 
(Mexico); 7, P. nigropilosus (Costa Rica); 8, P. reconditus (Nicaragua, holotype); 9, P. simulans (Panama). 

VOLUME 2, NUMBER 1, 1993 



1 mm 

Figs. 10-19. Pseudomyrmex ferrugineus group, workers, full-face dorsal (=frontal) view of head with pilosity 
shown in outline (except on mandibles); Fig. 19 includes a lateral view of head. 10, P. satanicus (Panama); 1 1, P. 
spinicola (Costa Rica); 12, P. peperi (Guatemala); 13, P. nigrocinctus (Costa Rica); 14, P. particeps (Costa Rica, 
holotype); 15, P. mixtecus (Mexico, holotype); 16, P.flavicomis (Nicaragua); 17, P. veneficus (Mexico); 18, P. 
ferrugineus (Mexico); 19, P.janzeni (Mexico, holotype). 



1 mm 

Figs. 20-29. Pseudotnyrmex ferrugineus group, workers, dorsal view of petiole paired with lateral view of 
mesonotum, propodeum, petiole and, in Fig. 28, postpetiole. Standing pilosity shown in outline. 20, P. satanicus; 
21, P. spinicola', 22, P. nigrocinctus', 23, P. particeps', 24, P. peperi; 25, P. flavicornis; 26, P. mixtecus; 27, P. 
ferrugineus; 28, P. veneficus', 29, P.janzeni. These are the same individuals illustrated in Figs. 10-19. 

VOLUME 2, NUMBER 1 , 1 993 




-i- spinicola, satanicus 
D other species 


3 1" 1 


-+ spinicola, satanicus 
D other species + + 

f V* 


+ + + D 




+H ,*f **** * g 

\ + 



/r + ffS^^n 


* + + +4- 

+ +++ ++ + tfj a 

+ + J.J. + [>. 


+ D 
+ * n 

m tflja 
=5SEj5i n 

i 1.1 

+ - ^fl?^ 


** &L 

f#ftl B o n 

+ + rft Jo b ^ 


a o 





a "3 


0.9 - 

ff fl 





0.8 - 


0.6 - 

01 D 

.8 1 

1.2 1.4 

0.7 - 

.7 0.9 1.1 1.3 

.* / 08 




0.7 - 

+- spinicola, satanicus 
D other species 


33 29 

0.28 - 

-i- spinicola, northern popns. 
X spinicola, southern popns. 

D D 

D satanicus 


3 n jl D n D 

0.27 - 

0.6 - 

o r a ' 

! B, 310 "fc ,,51*0 



' B a ^a * *^a i? 

0.26 - 

X D 

+ < 

3 0.5 - 

S ^ "Jg 

?|^o D * a 

* 0.25 - 

X X \ *** * " 

o a$8> =h a a a 

D a 

X xxx X x "x-t, 

0.4 - 


+ + + +* 

0.24 - 

+ n 

a TD 

cPn* 1 D 

+ + + + "*"+* + 

x a 

D ""b D 44. 

+ +1|. + + + > + 

0.23 - 

x + x + o 


0.3 - 

rjDD + + 

+ + + >+* + + * + t 

x D 

0.2 - 


0.22 - 



7 0.9 

1.1 1 

3 0. 
> 0.82 -i 

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 

94 0.98 1 .02 1 .06 1.1 1.14 1.18 1 .22 1 .26 


1.35 - 

+ spinicola, northern popns. 
X spinicola, southern popns. 
D satanicus 



35 a- 

0.78 - 
0.76 - 

workers D 
+ spinicola, northern popns. a D 
X spinicola, southern popns. 
D satanicus a D 

1.3 - 

a o 

; o =^ 

0.74 - 


1.25 - 

+ x 

0.72 - 



+ D o 

0.7 - 

"xx + t 

1.2 - 

x XX 

0.68 - 

* \ a% o* 

D D 


1.15 - 

x* X x + * 

0.66 - 


xx + 

0.64 - 

x x x x x + 

x # x + + 

1.1 - 

X + + 

0.62 - 

X + 

X + 

0.6 - 

+ + 

1.05 - 


0.5B - 


1 - 


0.56 - 

X X 



0.54 - 
0.52 - 



4 0.98 1.02 1.06 1.1 

1.14 1.18 1.22 1.26 


4 0.98 1 .02 1 .06 1.1 1.14 1.18 1 .22 1 .26 



36 5 

+ peperi 


1.05 - 

workers a D 
-i- peperi n o 

1.4 - 

X nigrocinctus, particeps 


X nigrocinctus, particeps a o aa 

D others 

i i * a a 

1 - 

D others ^ D^D D tf * 

1.3 - 


0.95 - 

B B ^gaB 

1.2 - 


"Jg." >s 

b^So? D 

0.9 - 

*:*/ !^^ aaZ 

0.85 - 

i + ^fi 

Wp tJ D 


X * A HrJra 

B^ D 


v v -H-* BC Cf[ri 

x x ** ag<* 


0.8 - 

4 + D ggiP n n D 

1 - 

"****** B" 

x4^ D "% 

0.75 - 

x *+j< + % ^ 
x x^f + ^"Q D a 

^rv * u Q 

0.7 - 

|^ X cP D D 

0.9 - 

V* x ao 


0.65 - 

x X 

0.8 - 

0.6 - 

Figs. 30-37. Scattergram plots of various metric measurements and indices in workers and queens of the 
Pseudomyrmex ferrugineus group, "other species" refers to all others in the P. ferrugineus group. 





O.BS - 


39 . 

x * 


O.8 - 

+ peperi 
X nigrocinctus, particeps 

a a 

0.58 - 

X x 

4- peperi 
X nigrocinctus, particeps 

D others 

O crf 

0.56 - 

jfffe x 

D others 

0.75 - 



0.54 - 

* x x 

0.7 - 

Hi tf n V-8 

0.52 - 

** D 


o SB,* o* # 

0.5 - 


D D Q, 

0.65 - 

+ + + 

D nSr^Jb a aa a D D 

to 0.48 - 


SO rfl 

0.6 - 


o a 3o cpogi 
n uSb^ o 

Q. 0.46 - 
0.44 - 

GO %OH a, 
O B. D^ n 9-J ^ 9iP 

0.55 - 
0.5 - 

fc<* x 

&' :-? 

ff BjB'tBBo 
a Cf a 

_OrP D 

-* 1 


0.42 - 
0.4 - 
0.38 - 

+ + + . 

+ + 

* D aDBo na 
.** D a a D 

0.45 - 



0.36 - 

+ * + 


x *x D on 

0.34 - 


t* DO 

0.7 0.9 

1.1 1.3 0.7 

0.9 1.1 1 



0.52 - 

****** * 

41 0.3 

workers D 
legend as in Fig. 39 a 

0.5 - 

* * ****** 


0.46 - 


0.48 - 

**.r ****** 

a a 

0.44 - 

* * * e a"<&> 

0.46 - 


an 'Sa 

0.42 - 

" *' 8b "n^o^ * 

0.44 - 

** * 

o a ^ fl D 

0.4 - 


*J oil? W '"t 

a ff ft jp ?f] ^3 a a 

0.38 - 


a %?PJ a D 

0.42 - 

0.4 - 

X X G D rO 

DLJ^ Gigjfjo 

* 0.36 - 


ego^ig^i 11 * D Q 

X x D C 

D ^ e T On 

0.34 - 

* * + 

oj CD t>t 6nj" 1 ^ 

0.38 - 


0.32 - 

Q o D 3ti P 

0.36 - 

> X X x 

G r3feOQ a D 

0.3 - 

*+ \ x 


0.34 - 

X x*x* X 

*J G^ o D G 

0.28 - 



Q D 

0.32 - 

QD t w 3 a B 

0.26 - 


0.3 - 

legend as in Fig. 39 



0.24 - 

Xx G 


0.7 0.9 

1.1 1.3 o.7 

0.9 1.1 1 



0.5 - 
0.49 - 

-I- particeps 
D nigrocinctus 



^~* 49 - 

+ particeps 
n nigrocinctus 


0.48 - 


0.48 - 


0.47 - 


0.47 - 


0.46 - 


0.46 - 


0.45 - 

0.45 - 


+ + 

G D 


+ + D 

0.44 - 

0.44 - 

G a D 

* a a 

0.43 - 


* a 

0.43 - 

+ D D D 

+ a a 

0.42 - 



0.42 - 

o a a 

D D 

0.41 - 

o D 

0.41 - 

a D D 

0.4 - 

0.4 - 




' ' ' 



0.74 - 
0.72 - 
0.7 - 

+ veneficus 
X mixtecus 
a flavicornis 



D aa 

ao a 

45 *- 

0.45 - 
0.44 - 
0.43 - 

-f- veneficus 
X mixtecus 
n flavicornis 


O.68 - 

o a 

0.42 - 

n Q D 

0.66 - 

a a n 

O D "- 1 

0.41 - 

D H D 

0.64 - 


0.4 - 


0.62 - 



0.39 - 

0.6 - 

^ a o D 

D.38 - 

tt 0.37 - 

X X 

0.58 - 

x * 

x a 

0.36 - 

x X 

0.56 - 

0.35 - 

x D 

0.54 - 

+ x 

0.34 - 

x x a 

0.52 - 

+ * + + X 

0.33 - 


0.5 - 

f + 

0.32 - 

* ++ + + 

0.48 - 

*+ D 

0.31 - 
0.3 - 


0.46 - 

0.29 - 

* + 


0.44 - 
0.42 - 

+ X 

0.28 - 

n 97 - 

x + 

Figs. 38-45. Scattergram plots of various metric measurements and indices in workers of the Pseudomyrmex 
ferrugineus group, "others" refers to all other species in the P. ferrugineus group. 

VOLUME 2, NUMBER 1, 1993 






+ veneflcus 

D D 

47 'Z\ 

queens D D 
+ veneflcus o 

0.95 - 

X mixtecus * a jp D 
O ferrugineus, flavicornis x x* x aoSjiBi 

0.54 - 

X mixtecus x x 
rj ferrugineus, flavicornis x n D 'rf 1 D 

0.9 - 

A janzeni 


0.52 - 

4 nigrocinctus , particeps x o a 

a a 

0.5 - 

& peperi D D a 

0.85 - 

**** a a a 

0.48 - 

* + D D _ a 

+ * A * 

DD 8 

0.8 - 

* * * A 

J 0.46 - 

* r+ * a ^o 

* t ** 

0.44 - 

* * + + D D 

0.75 - 

9 a 

I ^* A A 

0.7 - 


0.42 - 

:k* * 


0.4 - 

** ** * 

0.65 - 

** * * 

0.38 - 

* * : 

0.6 - 
55 - 


0.36 - 
n TA 

* / 

0.9 1.1 

1.3 1.5 0.75 0.85 0.95 1.05 1.15 

. _ . ~ 

0.42 - 
0.41 - 

workers + 
+ janzeni 
D Mexican ferrugineus 


1.02 - 

-h flavicornis D D * 
D ferrugineus + +. 

0.4 - 

* a en 

1 - 

a o + 

0.98 - 

D 4- 

0.39 - 

D _ 

0.96 - 

a a a D 

0.38 - 


D gl 

0.94 - 

a D o a 

0.37 - 


+ D 

0.92 - 

n 4- 

0.36 - 

* Q 
D D 

* 0.9- 


0.35 - 

+ + 


0.88 - 



J a 

0.86 - 


0.34 - 



D g 

0.84 - 


0.33 - 



0.82 - 

0.32 - 


0.8 - 


0.31 - 

0.3 -I 


0.78 - 
n 7K 

4 A* 


0.92 0.94 0.96 0.98 

1 1.02 1.04 1.06 1.08 1.1 1.12 1.14 0.96 1 1.04 1.08 1.12 1.16 


0.6 - 
0.59 - 

-* flavicornis 
P ferrugineus 




3 _L 0.53 - 
0.52 - 


0.58 - 


0.51 - 

* * D 

0.57 - 

D *+ + * 

0.5 - 

* t * , 

O.56 - 

? Q + 

0.49 - 

o a e 

0.55 - 

* i 

3 On D * 4-+* + 

0.48 - 

a S D ** + 

0.54 - 


D D n * 

0.53 - 

a ao 

B " * + 


B D B n n + * * 

0.52 - 

tb ^ 

W 0.46 - 

i a cP D * 

O.51 - 

a o 


0.45 - 

DQC tD D a a 

0.5 - 

o o D Q 


O.44 - 

D u 

0.49 - 

a a o 

0.43 - 

D D P S o 

0.48 - 


0.42 - 

O.47 - 

0.41 - 

workers D a 

0.46 - 
0.45 - 


0.4 - 

-t- flavicornis D a a 
D ferrugineus 

0.92 0.96 1 

1 ' 1 1 1 1 1 1 1 1 w.j [ [ 1 1 1 1 1 1 1 1 1 1 p 1 1 
1 .04 1 .08 1.12 1.16 1 .2 0.8 0.82 0.84 0.86 0.88 0.9 0.92 0.94 

HW Cl 
n R -^ 

0.82 - 

+ spinicola 


"x H- gracilis 

0.8 - 
0.78 - 
0.76 - 

D D a 

X satanicus 
D ferrugineus complex 
A others 


0.75 - 
0.7 - 

X nigropilosus 
\ x x x x Q opaciceps 
x x x x A simulans 
x reconditus 


0.65 - 

* A 

0.74 - 

D n 

If f x ^x x X 

** A * 

0.72 - 

* A 

DD n O X X 

D a u + * x 

5 ' 6 - 

A * * 

0.7 - 


83 go w^ff + * + 

+ + + * 

A A A r 

a cD ff^ -iP 

0.55 - 

+ + * + 

0.68 - 

A A f* 


/> *\ **,** 

0.66 - 


*" * + 4- 

0.5 - 

0.64 - 

D ^ * + .> + . * + *v* + 

0.45 - 

0.62 - 

+ * 

fi 1 

0.6 - 

A A 

+ + 4. 

O.4 - 


Figs. 46-53. Scattergram plots of various metric measurements and indices in Pseudomyrmex workers and queens. 
46-52, P. ferrugineus group; "others" refers to all other species in the P. ferrugineus group; "P. ferrugineus 
complex" refers to a complex of five species: ferrugineus, flavicornis, janzeni, mixtecus and veneficus; 53, P. 
gracilis group. 




The following key includes all species of Pseudomyrmex which have been found inhabiting swollen- 
thorn acacias in Mexico, Central America, or Colombia. Pseudomyrmex ants can be distinguished from 
others by their possession of a distinct postpetiole (i.e. "waist" consists of two nodes), well developed 
sting, relatively large eyes (eye length more than one-third head length), and short antennal scapes (one 
half head width or less). In the key below, species of Pseudomyrmex which are believed to be obligate 
inhabitants of acacia are in bold print. These species are typically rather aggressive (but this is not true 
of P. subtilissimus or P. nigropilosus), while the remaining facultative inhabitants are timid, generalist, 
stem-nesting Pseudomyrmex which usually occupy swollen-thorn acacias only sporadically. 
Couplets 11-19 cover the P. ferrugineus group, the principal group of obligate acacia-ants and the 
focus of this study. Taxonomic comments on the other acac/a-inhabiting species are presented in a later 
section of the paper (pp. 153- 162). Worker sizes exclude nanitic workers, i.e. the first-emerging 
miniature workers associated with colony-founding queens. 

1 . Standing pilosity very sparse on the head, including the gula (underside), and on the mesosoma; 1 ,0, 
and 0-1 pairs of erect setae on the pronotum, mesonotum, and propodeum, respectively, of the 
worker 2 

Standing pilosity common to abundant on most parts of the body, including the gula and mesosoma; 
worker usually with more than 10 standing hairs visible in outline on the mesosoma dorsum, not 
arranged in isolated pairs 4 

2. Very small, light brown species (worker and queen HW < 0.60), with elongate head (CI < 0.66) and 
low, dorsally flattened petiole (PLI < 0.76) (Nicaragua, Costa Rica) subtilissimus (Emery) 

Larger species (worker and queen HW > 0.70), with broader head (CI > 0.70) and higher petiole (PLI 
> 0.80) (Figs. 1,2) 3 

3. Smaller species (worker and queen HW < 1.00), with posterodorsally angulate petiole (Fig. 2) 
(Mexico to Colombia) ita (Forel) 

Larger species (worker and queen HW> 1.15), with posterodorsally rounded petiole (Fig. l)(Mexico 
to Ecuador, Brazil) boopis (Roger) 

4. Head with scattered, fine punctulae on a smooth, shiny background; punctulae on upper third of head 
separated by several times their diameters or more 5 

Head opaque to sublucid, more coarsely and densely punctulate, the punctulae subcontiguous on 
most parts of the head 6 

5. Larger species (HW> 1.20), with broad head (CI 1.12) and abundant long pilosity (Fig. 3) (Mexico 
to Argentina, Brazil) kuenckeli (Emery) 

Small species (HW < 0.72), with elongate head (CI 0.80) and shorter, sparser pilosity (Fig. 4) 
(Mexico) hesperius, sp.nov. 

6. Eyes relatively large and elongate (e.g. Fig. 5), eye length more than one-half head length (worker 
and queen REL 0.52-0.65); pronotum laterally submarginate; outer surfaces of tibiae usually with 
standing pilosity (may be very short); larger species, worker HW > 1.20; palp formula 6,4 7 

Eyes smaller (Figs. 10-19), usually less than one-half head length (worker and queen REL 0.38-0.50); 
pronotum laterally rounded; outer surfaces of tibiae without standing pilosity; medium-sized species, 
worker HW < 1.28; palp formula 5,3or 4,3 (ferrugineus group) 11 

7. Petiole long and slender, with a well developed anterior peduncle (worker and queen PLI 0.42-0.57) 

VOLUME 2, NUMBER 1 , 1 993 1 31 

(Figs. 5,6) 8 

Petiole less elongate, with a short anterior peduncle (PLI > 0.59) (Figs. 7-9, 53) 9 

8. Head densely punctulate-coriarious, presenting a matte appearance; head and mesosoma black, with 
a contrastingly pale orange petiole, postpetiole, and gaster; petiole very slender, worker PLI 0.42-0.47 
(Figs. 5, 53) (southern Mexico, Guatemala) opaciceps, sp. nov. 

Head densely punctulate but retaining a subopaque to sublucid (not matte) appearance; color variable 
but without the preceding pattern in Mexico or Guatemala; petiole usually less slender, worker PLI 
0.46-0.57 (Figs. 6, 53) (throughout the Neotropics) gracilis (Fabricius) 

9. Larger species (worker HW 1.47- 1.54, queen HW 1.66), with broad head (worker CI 1.00- 1.02, queen 
CI 0.92) (Nicaragua) reconditus, sp. nov. 

Smaller species (worker HW 1. 21-1.41, queenHW 1.15-1. 36); head more elongate (worker CI 0.84- 
0.90, queen CI 0.77-0.80) 10 

10. Standing pilosity short, pale and inconspicuous (Fig. 9); pronotum sharply margined laterally; petiole 
longer, worker PLI 0.61-0.66, queen PLI 0.63-0.68; color black (Panama) simulans Kempf 

Standing pilosity long and conspicuous, with long curved black setae arising from the propodeum and 
petiole (Fig. 7); pronotum with blunter lateral margination; petiole short and high, worker PLI 0.69- 
0.77, queen PLI 0.68-0.75; color variable, usually pale or bicolored (Mexico to Costa Rica) 

nigropilosus (Emery) 

1 1 . Median clypeal lobe of worker concave, with sharp lateral angles or teeth (Figs. 10, 1 1); legs long in 
relation to body size (Figs. 30, 3 1 ); larger species (worker HW > 0.92, worker LHT > 0.88, queen HL 
> 1.40, queen LHT > 1.05); frontal carinae closely contiguous, worker FCI2 0.24-0.42 (Fig. 32); 
propodeum punctulate to coriarious-imbricate, posterolateral portions sublucid with little or no 
overlying, coarse, rugulo-punctate sculpture 12 

Median clypeal lobe of worker laterally rounded or subangulate (without sharp angles or teeth) (Figs. 
12-19); legs shorter in relation to body size (Figs . 30, 3 1 ); size variable but if as large as the preceding 
(worker HW > 0.92, etc.) then frontal carinae relatively well separated, worker FCI2 > 0.43 (Fig. 32), 
and posterolateral portions of propodeum opaque to subopaque, overlain by coarse (although often 
weak and ill-defined) rugulo-punctate sculpture 13 

1 2. Larger species (worker HW > 1 .09, queen HW > 1 .20); head broader, its posterior margin straight and 
rounding rather sharply into the sides (Figs. 10, 34); median clypeal lobe of worker longer and 
narrower (Fig. 33); worker with a conspicuous, pit-like impression on midline of head, anterior to the 
median ocellus; palp formula 4,3 (Panama) satanicus (Wheeler) 

Smaller species (worker HW 0.94-1. 15, queenHW 0.94 - 1.14), with head a little less broad and its 
posterior margin rounding more gently into the sides (Figs. 10, 34); median clypeal lobe of worker 
notably shorter and broader (Fig. 33); worker usually lacking a pit-like impression on mid-line of 
head; palp formula almost invariably 5,3, rarely 5p4,3 (Honduras to Colombia 

spinicola (Emery) 

13. Smaller species (worker HW 0.74-0.90, queen HW 0.76-0.85); head, propodeum, and petiole more 
elongate, for a given head width (Figs. 36-38) 14 

Larger species (worker HW 0. 85- 1 .2 1 , queen HW 0. 84- 1.19); head, propodeum, and petiole shorter, 
for a given head width (Figs. 36-38) 16 

14. Petiole and postpetiole very broad (worker PWI 0.63-0.75, worker PWI3 0.33-0.46, worker PPWI 
1.41-1.83; queen PWI2 0.69-0.78) (Figs. 40, 41), the petiolar node with conspicuous posterolateral 
angles, in dorsal view (Fig. 24); head very finely and densely punctulate-coriarious, presenting a 
matte (opaque) appearance; palp formula 4,3 (Mexico to Nicaragua) peperi (Forel) 

Petiole and postpetiole relatively narrow (worker PWI 0.49-0.61 , worker PWI3 0.50-0.61, worker 
PPWI 1 .03- 1 .30; queen PWI2 0.57-0.63), the petiolar node without conspicuous posterolateral angles 


(Figs. 22,23); head densely punctulate, sublucid to subopaque, but without a matte appearance; palp 
formula 5,3 15 

15. Workers and queens light orange-brown, with a fuscous patch on anterior third of abdominal tergite 
IV (first gastric tergite); eyes relatively short (worker EL/LHT 0.56-0.61, queen REL2 0.58-0.66) 
(Figs. 13, 42, 43); queen head less elongate (queen CI 0.67-0.72) (Guatemala to Costa Rica) 

nigrocinctus (Emery) 

Workers and queens entirely dark brown; eyes longer (worker EL/LHT 0.59-0.64, queen REL2 0.69- 
0.70) (Figs. 14, 42, 43); queen head more elongate (CI 0.61, in the two known specimens) (Costa 
Rica) particeps, sp. nov. 

16. Small species (worker HW 0.85-0.95, queen HW 0.84-0.96) with head, gaster, and at least part of 
mesosoma very dark brown to black; body pubescence dense, decumbent to suberect, and conspicu- 
ous, especially on the petiolar node (Fig. 28); standing pilosity often (not always) sparse; head weakly 
shining (western Mexico) veneficus (Wheeler) 

Body pubescence dense but predominantly appressed, petiolar node without conspicuous suberect 
pubescence; usually larger (worker HW 0.89-1.21, queen HW 0.96-1.19) with more conspicuous 
standing pilosity; color and head sculpture variable 17 

17. Head and gaster (typically also mesosoma) very dark brown to black; head densely punctulate and 
opaque 18 

Body lighter in color: light orange-brown to medium brown, rarely dark brown; head at least weakly 
sublucid between ocelli and upper margin of the compound eye 19 

18. Smaller species, worker HW 0.89-1.03, queen HW 0.96-1.01; petiole relatively longer and higher 
(Figs. 44-47) (southern Mexico) mixtecus, sp. nov. 

Larger species, worker HW 0.99-1.21, queen HW > 1.10; petiole relatively shorter and lower (Figs. 
44-47) (Guatemala to Costa Rica) .flavicornis (F. Smith) 

19. Head and mesosoma light orange-brown, the gaster similar or slightly darker; underside of head (gula) 
with conspicuous suberect pubescence (Fig. 19); profile of worker mesosoma as in Fig. 29; smaller 
species (worker HW 0.93-1.03, queen HW 0.96-1.00) with shorter, higher petiole (Figs. 46-49) 
(western Mexico) .janzeni, sp. nov. 

Gaster (and usually head) medium to dark brown, mesosoma variable; gular pubescence usually more 
appressed and inconspicuous; in profile worker mesosoma usually with basal face rounding more 
gradually into declivitous face (Fig. 27); size variable but larger on average (worker HW 0.92- 
1 . 15,queen HW 0.92-1 . 12), with longer and lower petiole (Figs. 46-49) (eastern and southern Mexico 
to Honduras) .ferrugineus (F. Smith) 


Although isolated acacia-ant males are unlikely to be encountered, the following key is offered as a 
supplement for determination of species in the P. ferrugineus group. It can be used to confirm worker- 
or queen-based identifications, but some couplets require examination of the male genitalia. 

1 . Posterior margin of subgenital plate (sternite IX) with a shallow (less than semicircular) concavity 
(Fig. 54); scape short, SI2 0.33-0.43, SL/HL 0.21 2 

Posterior margin of subgenital plate (sternite IX) with a deep, semicircular concavity (Fig. 55); scape 
longer, SI2 0.43-0.56, SL/HL 0.22 3 

2. Paramere, in lateral view, with a slender finger-like mediodorsal lobe and angulate posteroventral 
corner (Fig. 57) particeps 

Paramere, in lateral view, with a stubbier mediodorsal lobe and more gently rounded posteroventral 

VOLUME 2, NUMBER 1, 1993 


corner (Fig. 56) nigrocinctus 

3. Scape and compound eye longer, relative to HW (SI 0.29-0.35; REL2 0.56-0.62 (n=6)); head 
narrower, CI 0.82-0.94, HW 0.81-0.95; lateral view of paramere as in Figs. 58a, 58b peperi 

Scape and compound eye shorter (SI 0.22-0.30, REL2 0.49-0.58); head broader, CI 0.94 and/or HW 

0.96; lateral view of paramere not as in Figs. 58a, 58b 4 

4. Paramere, in lateral view, with posterodorsal corner well separated from mediodorsal lobe (Figs. 59- 
60) 5 

Paramere, in lateral view, with posterodorsal corner bent upward and enclosing a space between itself 
and the mediodorsal lobe which is subequal to the area of the latter (Figs. 61-65) 6 

5. Lateral view of paramere as in Figs. 59a and 59b: mediodorsal lobe relatively broad and partly 
enclosing a space between itself and the posterodorsal corner; larger species, HW 1.06-1.09 
(n=5) satanicus 

Paramere typically as in Fig. 60a, with mediodorsal lobe more slender and more distant from 
posterodorsal corner (Fig. 60b depicts a less typical male, from Colombia); smaller species, HW 0.92- 
1.05 (n=12) spinicola 

6. Mediodorsal lobe of paramere stout, directed more or less dorsally (Figs. 61, 62) 7 

Mediodorsal lobe of paramere more slender and directed posterodorsally (Figs. 63-65) 8 

7. Body pubescence dense and conspicuous, suberect on dorsum of head, propodeum and petiole; 
smaller species, HW 0.79-0.88 (n=7) veneficus 

Body pubescence less dense and less conspicuous, predominantly appressed or decumbent on the 
propodeum and petiole; larger species, HW 0.88-0.97 (n=6) mixtecus 

8. Smaller species, HW 0.93-0.96 (n=6) janzeni 

Larger species, HW 0.99-1.19 (n=22) .ferrugineus andflavicornis 


Worker, diagnosis. Medium sized species (HW 
0.74- 1 .26, HL 0.86- 1 .42); head varying from mod- 
erately elongate to rather broad (CI 0.75-0.97), with 
relatively short eyes (REL 0.39-0.50, REL2 0.45- 
0.62) (Figs. 10-19). Masticatory margin of man- 
dible with 6, rarely 7, teeth, MD8/MD9 0.70; 
mesial tooth on basal margin notably closer to 
apicobasal angle than to proximal tooth, MD4/ 
MD5 0.74. Palp formula 5,3, reduced to 4,3 in two 
species. Anterior margin of median clypeal lobe 
somewhat blunt-edged, in dorsal view convex, 
straight or concave, laterally rounded or with sharp 
angles. Frontal carinae separated by about basal 
scape width in most species but more closely con- 
tiguous in two (FCI 0.03-0. 10, FCI2 0.24-0.75, ASI 
0.52-0.73), fusing anterolaterally with antennal 
sclerites. Funicular segments II and III about as 
broad as long (FLI 1 .46-2.45). Profemur slender (FI 
0.35-0.41). Pronotum laterally rounded. Metanotal 
groove well marked (MPI 0.04-0.09). Basal and 
declivitous faces of propodeum moderately well 

differentiated and subequal in length (PDI 0.94- 
1.30), in profile the juncture between the two 
subangulate or gently rounded (Figs. 20-29). Peti- 
ole relatively long (PL/HL 0.44-0.63), always much 
longer than high or wide (PLI 0.47-0.7 1 , PWI 0.46- 
0.75), small anteroventral tooth present; in two 
species anterior peduncle of petiole weakly differ- 
entiated and posterolateral corners of petiolar node 
not expanded (these are presumably the 
plesiomorphic conditions in the group), in other 
species petiole with distinct anterior peduncle and 
with expanded, (sub)angulate posterolateral cor- 
ners. Postpetiole broader than long (PPWI 1.03- 
1.85), with small anteroventral tooth. Body sculp- 
ture varying from densely punctulate or punctulate- 
coriarious to coriarious-imbricate, the integument 
sublucid to opaque; dorsum of head never with 
extensive smooth, shiny interspaces (punctulae 
usually separated by their diameters or less); 
propodeum of some species overlain by a coarser 
but weak rugulo-punctate sculpture. Standing pi- 
losity common, present on the scapes, head, entire 
mesosoma dorsum (10 or more standing hairs vis- 
ible in profile), petiole, postpetiole and gaster, 










1 mm 


Figs. 54-66. Pseudomyrmexferrugineus group, male terminalia. Figs. 54-55: sternite IX; Figs. 56-65 : left paramere, 
lateral view, caudal end to right; Fig. 66: left paramere, mesial view. 54, P. particeps (Rincon, Costa Rica); 55, P. 
mixtecus (near Tehuantepec, Mexico); 56, P. nigrocinctus (lOmi. NW Liberia, Costa Rica); 57, P. particeps 
(Rincon, Costa Rica); 58, P. peperi (58a: 3km ENE Chiapa de Corzo, Mexico; 58b: Nueva Ocotepeque, Honduras); 
59, P. satanicus (59a: 3mi. SW Gatun Dam, Panama; 59b: Marajal, Panama); 60, P. spinicola (60a: Madden Dam, 
Panama; 60b: Aracataca, Colombia); 61, P. mixtecus(61&: 57. 8mi. S Chilpancingo, Mexico; 61b: near Tehuantepec, 
Mexico); 62, P. veneficus (5km E Chamela, Mexico); 63, P.flavicornis (63a: Rio Oro, Costa Rica; 63b: 3.6mi. W 
Choluteca, Honduras); 64, P. janzeni (64a: 60mi. SE Acaponeta, Mexico; 64b: 4mi. E San Bias, Mexico); 65, P. 
ferrugineus (65a: Escuintla-Cd. Guatemala, Guatemala; 65b: 10.8mi S Pichucalco, Mexico); 66, P. ferrugineus 
(10.8mi S Pichucalco, Mexico). 

VOLUME 2, NUMBER 1, 1993 


absent from the extensor faces of tibiae. Appressed 
pubescence dense on most of body, including head 
and abdominal tergite IV. Color varying from light 
yellow- or orange-brown to black. 

Queen diagnosis. Similar to worker except for 
caste-specific differences. Larger in size (HW 0.76- 
1.36, HL 1.05-1.81), head more elongate (CI 0.60- 
0.80). Ocular indices differing slightly: REL 0.38- 
0.48, REL2 0.51-0.70. Median clypeal lobe nar- 
rower and more protruding, anterior margin convex 
or straight, laterally rounded or subangulate. Peti- 
ole and postpetiole generally more slender (PL/HL 
0.57-0.72, PLI 0.43-0.63, PWI 0.47-0.67, PPWI 
1.06-1.50). Forewing with 2 cubital cells. 

Male, diagnosis. Head varying from longer 
than broad to slightly broader than long (CI 0.82- 
1.04 in a sample of 70 males belonging to all 
species); compound eye large, prominent (REL2 
0.49-0.62). Mandibles with 8+ teeth or denticles on 
masticatory margin. Palp formula as in females, 
but somewhat more variable (males with 5p4,3 
commoner than in workers or queens). Surface of 
median clypeal lobe convex, its anterior margin 
subtriangular in shape (dorsal view) with sides 
converging medially to a rounded point. Petiole 
and postpetiole more slender than in workers (PLI 
0.40-0.55, PWI 0.35-0.51) and simpler in shape. 
Posterolateral corners of sternites IV- VIII not nota- 
bly protruding ventrally. Subgenital plate (sternite 
IX) with a conspicuous posteromedial concavity 
(Figs. 54, 55). Posterior margin of pygidium (terg- 
ite VIII) convex, directed posteroventrally. 
Paramere with several characteristic features: a 
finger-like, posterodorsally directed mediodorsal 
lobe; angulate or expanded posterodorsal extrem- 
ity; and mesial dorsoventral ridge which joins the 
mediodorsal lobe posteriorly. Aedeagus with ex- 
panded posterodorsal corner, a medial protrusion 
on the posterior margin,numerous small teeth (15+) 
on the posterior margin, and on the outer face a 
raised ridge curving posterodorsally from a basal 

Comments. Workers and queens of the P. 
ferrugineus group can be distinguished from all 
other Pseudomyrmex by their possession of the 
following combination of traits: mandibles with 6- 
7 teeth; palp formula 5,3 or 4,3; standing pilosity 
common on mesosoma dorsum but absent from 

external faces of tibiae; worker metanotal groove 
conspicuously impressed; and head densely 
punctulate, sublucid to opaque. The relatively 
short eyes (worker REL 0.50, queen REL 0.48) 
and slender petiole (worker PLI 0.71, queen PLI 
0.63) are also characteristic. Among the eight 
other major species groups of Pseudomyrmex 
(diagnosed in Ward, 1 989) only the P. viduus and P. 
oculatus groups have workers and queens approach- 
ing these conditions. Those of the P. viduus group 
have a shinier head, a shorter and more robust 
petiole (worker PLI > 0.70, worker PWI > 0.70), 
and standing pilosity on the tibiae (reduced in one 
species), while workers and queens of the P. oculatus 
group have a palp formula of 6,3 (reduced to 5,3 
only in smallest species with worker and queen HW 
< 0.67), tectiform and sharp-edged median clypeal 
lobe with a broadly convex margin (dorsal view), 
elongate eyes (worker REL 0.48-0.6 1 , worker REL2 
0.62-0.86, queen REL 0.43-0.57, queen REL2 0.68- 
0.89), and short petiole (worker PLI 0.67-1.06, 
queen PLI 0.57-0.94). Among taxonomically iso- 
lated species not belonging to one of the major 
species groups, P.fervidus (F. Smith) bears perhaps 
the closest phenetic resemblance to the P. 
ferrugineus group, but its workers and queens can 
be distinguished by their shinier and less densely 
punctulate head, shorter petiole (worker PLI 0.71- 
0.76, worker PL/HL 0.41-0.44 (n=9); queen PLI 
0.65, queenPL/HL 0.49), and standing pilosity on 
the outer faces of the tibiae. In addition the queens 
of P. fervidus have a distinctive, pointed median 
clypeal lobe not seen in P. ferrugineus group queens. 

Males of the Pseudomyrmex ferrugineus group 
can be characterized by their palp formula, medi- 
ally subangulate clypeal lobe, emarginate subgenital 
plate, configuration of the paramere, and shape of 
the aedaegus. They are approached most closely in 
this combination of traits by males of P. haytianus 
(Forel) and two undescribed Central American 
species (P. sp. PSW-02 and P. sp. PSW-54) al- 
though, curiously, the workers and queens of those 
species do not bear a close resemblance to those of 
the P. ferrugineus group. 

All species in the P. ferrugineus group are 
obligate inhabitants of Central American swollen- 
thorn acacias, a biological trait not characterizing 
any other species group of Pseudomyrmex, al- 



though a few species in the otherwise quite differ- 
ent P. gracilis group and one species in the P. 
subtilissimus group have independently developed 
an obligate association with the acacias. 

Distribution. Members of the P. ferrugineus 
group are found from eastern (San Luis Potosi, 
Tamaulipas) and western (Sinaloa) Mexico south 
through Central America to northern Colombia 
(Fig. 67). Although no single species spans the 
entire range of the group, their collective distribu- 
tion is virtually identical to that of the swollen- 
thorn acacias (compare Fig. 67 with Janzen 1974:3). 

Synonymic List of Species 

P. ferrugineus (F. Smith 1877) Mexico to Hondu- 

= P.fulvescens (Emery 1890) (Ward 1989) 
= P. canescens (Wasmann 1915) (Ward 1989) 
= P. wasmanni (Wheeler 1921) (replacement 

name for canescens) 

= P. bequaerti (Wheeler 1942) (Ward 1989) 
= P. saffordi (Wheeler 1942) (Ward 1989) 
= P. vesanus (Wheeler 1942) (Ward 1989) 
= P. bequaerti (Enzmann 1945) (Brown 1949) 
= P. honduranus (Enzmann 1945) (Ward 1989) 

P.flavicornis (F. Smith 1877) Guatemala to Costa 


= P. belti (Emery 1890) (Ward 1989) 
= P. obnubilus (Menozzi 1927a) (Ward 1989) 
= P.fellosus (Wheeler 1942) (Ward 1989) 

P. janzeni Ward, sp. nov. Mexico 

P. mixtecus Ward, sp. nov. Mexico 

P. nigrocinctus (Emery 1890) Guatemala to Costa 


= P. alfari (Forel 1906) syn. nov. 
= P. bicinctus (Santschi 1922) syn. nov. 
= P. peltatus (Menozzi 1927) syn. nov. 

P. particeps Ward, sp. nov. Costa Rica 

P. peperi (Forel 1913) Mexico to Nicaragua 
= P. convarians (Forel 1913) (Ward 1989) 
= P. saffordi (Enzmann 1945) (Ward 1989) 

P. spinicola (Emery 1890) Honduras to Colombia 
= P. atrox (Forel 1912) syn. nov. 
= P. gaigei (Forel 1914) syn. nov. 
= P. infernalis (Wheeler 1942) syn. nov. 
= P. scelerosus (Wheeler 1942) syn. nov. 
= P. infernalis (Enzmann 1945) (Brown 1949) 

= P. scelerosus (Enzmann 1945) (Brown 1949) 
P. satanicus (Wheeler 1942) Panama 
P. veneficus (Wheeler 1942) Mexico 

= P. venificus (Enzmann 1945) (Brown 1949) 


Pseudomyrmex ferrugineus (F. Smith 1877) 
(Figs. 18,27,65,66,70) 

Pseudomyrma ferrugineaF. Smith 1877:64. Lec- 
totype worker, Mexico (BMNH) [Examined]. 

Pseudomyrma beltiracefulvescens Emery 1 890:64. 
Lectotype worker, Guatemala (Beccari) (MCSN) 
[Examined] [Synonymy by Ward 1989:437; see 
also Janzen 1967b:391]. 

Pseudomyrma canescens Wasmann 1915:321. 
Syntype workers, Tampico, Mexico (Brakhoven) 
(MCSN, MCZC) [Examined] [Synonymy by 
Ward 1989:437]. 

Pseudomyrma wasmanni Wheeler 1921:92. Re- 
placement name, now unnecessary, for P. 
canescens Wasmann 1915 (nee F. Smith 1877). 

Pseudomyrma belti subsp. bequaerti Wheeler 
1942:164. Lectotype worker, Puerto Castilla, 
Honduras (J. Bequaert) (MCZC) [Examined] 
[Synonymy by Ward 1989:437]. 

Pseudomyrma belti subsp. saffordi Wheeler 
1942:162. Lectotype worker, Chicoasen, 
Chiapas, Mexico (G. N. Collins) (MCZC) [Ex- 
amined] [Synonymy by Ward 1989:437]. 

Pseudomyrma belti subsp. vesana Wheeler 
1942:163. Holotype (unique syntype) worker, 
Cordoba, Mexico (F. Knab) (MCZC) [Exam- 
ined] [Synonymy by Ward 1989:437]. 

Pseudomyrma belti subsp. bequaerti Enzmann 
1945:80. Syntype workers, Puerto Castilla, 
Honduras (J. Bequaert) (MCZC) [Examined] 
[Objective synonym of P. belti bequaerti 
Wheeler; Brown 1949:42]. 

Pseudomyrma kuenckeli var. hondurana Enzmann 
1945:87. Lectotype worker, Honduras (Bates) 
(MCZC) [Examined] [Synonymy by Ward 

Pseudomyrmex ferruginea [sic] (F. Smith); Janzen 

Pseudomyrmex ferrugineus (F. Smith); Kempf 

VOLUME 2, NUMBER 1, 1993 


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Worker measurements (n = 69). HL 0.99- 1.33, 
HW 0.92-1.15, MFC 0.054-0.108, CI 0.81-0.94, 
REL 0.42-0.48, REL2 0.48-0.54, OOI 1.39-3.16, 
VI 0.60-0.78, FCI 0.054-0.101, SI 0.41-0.46, SI2 
0.79-0.91, NI 0.61-0.72, PLI 0.54-0.69, PWI 0.56- 
0.73, PPWI 1.34-1.70. 

Worker diagnosis. Medium-sized species (HW 
> 0.91; LHT 0.75-1.06) with broad head (CI > 
0.80); anterior margin of median clypeal lobe straight 
or weakly concave, rounded laterally; palp formula 
5,3; frontal carinae well separated (FCI > 0.05) and 
median lobe of antennal sclerite not strongly ex- 
posed (FCI2 0.45-0.69); mesosomal profile typi- 
cally as in Fig. 27, with mesonotum notably in- 
clined and with basal face of propodeum rounding 
gradually into declivitous face, but deviations from 
this pattern occur; petiole relatively short, high and 
wide (see relevant metrics: PLI, PWI), with a dis- 
tinct anterior peduncle (PWI3 0.36-0.50); postero- 
lateral angles of petiole moderately developed but 
not as pronounced as in P. peperi (compare Figs. 24 
and 27) ; postpetiole broad. Head densely punctulate, 
predominantly opaque or subopaque but at least 
weakly shining on upper third of head between 
ocelli and compound eye; mesosoma punctulate to 
punctulate-coriarious, subopaque to sublucid; pos- 
terior portions of propodeum opaque to subopaque 
and usually overlain by larger but weak, irregular 
punctures or rugulae. Petiole, postpetiole and gaster 
with fine piligerous punctures, sublucid. Standing 
pilosity common; pubescence dense but fine and 
appressed on most surfaces. Color variable, from 
light reddish- or yellowish-brown to very dark 
brown, gaster (and usually head) somewhat darker 
than the mesosoma; mandibles, scapes, fronto- 
clypeal complex, and apices of legs usually lighter. 

Comments. Workers and queens of P. 
ferrugineus can be recognized by features of head 
morphology (laterally rounded median clypeal lobe, 
well separated frontal carinae and correspondingly 
limited exposure of the median lobes of the anten- 
nal sclerites, and moderately broad worker head; 
see Fig. 1 8), head sculpture (densely punctulate and 
(sub)opaque, but weakly shining on upper third of 
head between the ocelli and compound eye), and 
coloration (variably brown, not black or orange- 

brown). This species is most likely to be confused 
with the allopatric P. janzeni and the partly sympa- 
tric P.flavicornis. See under those species for more 
specific discussion. 

Distribution and biology. P. ferrugineus is 
distributed from eastern and southern Mexico to El 
Salvador and Honduras (Fig. 70). It is a common 
species and colonies have been recorded from all 
swollen-thorn acacia species growing within its 
range, i.e. Acacia chiapensis, A. collinsii, A. cookii, 
A. cornigera, A. gentlei, A. globulifera, A. hindsii, 
A. janzenii, A. mayana and A. sphaerocephala. P. 
ferrugineus is usually monogynous (Janzen 1967b, 
1973) but a few alcohol nest series from Guate- 
mala, belonging to apparently mature colonies (as 
judged by the presence of alates), contained more 
than one dealate queen. Janzen (1966, 1967b) 
conducted a massive experimental study of the 
interaction between P. ferrugineus and Acacia 
cornigera in Mexico, and the results of these ex- 
periments, together with copious additional obser- 
vations by Janzen, showed conclusively that the 
ants protect the acacia from herbivores and compet- 
ing plants (especially vines). P. ferrugineus was 
also the subject of a study on kinship and nestmate 
recognition among workers (Mintzer 1982; Mintzer 
et al. 1985) which demonstrated a worker-based 
and probably inherited component to colony odor. 
Statements about the biology of "P. ferruginea" 
from regions south of El Salvador and Honduras 
(e.g. Janzen 1983) refer to a different species, P. 

Material examined (AMNH, BMNH, CASC, 

BEUZEBelize: 2.2mi W Belize, Chetumal 
(D.HJanzen); 3.8mi NW Belize, Chetumal 
(D.H.Janzen); 4.9mi SW Belize, Cayo 
(D.HJanzen); Belize (Baker; c.u.); Manatee [River] 
(J.D.Johnson; c.u.); nr. Belize (N.L.H.Krauss); 
Cayo: 36.1mi SW Belize (D.H.Janzen); 36.1mi 
[S]W Belize (U.Kansas Mex.Exped.); El Cayo 
[=San Ignacio] (N.L.H.Krauss); Pine Mtn. Ridge, 
Mecal R., 415m (G.D.Alpert); San Ignacio 
(S .E.Schoenig) ; Corozal: 1 3 .5mi S Sta.Elena (Lou- 
isville) (D.H.Janzen); 15mi S Sta.Elena (Louis- 
ville) (D.H.Janzen); Orange Walk: 5mi SE Orange 

VOLUME 2, NUMBER 1, 1993 


Walk, Belize (D.H.Janzen); Toledo: Punta 
Gorda (H.Broomfield). 

EL SALVADOR Chalatenango: 4.7mi NW La 
Palma, 880m (D.H.Janzen); 5.5mi SE La Palma, 
11 30m (D.H.Janzen). 

GUATEMALA A Ita Verapaz'. San Joaquin, nr. 
San Cristobal Verapaz, 1080m (D.H.Janzen); Trece 
Aguas (Schwarz & Barber); Chimaltenango: 
Yepocapa (H.T.Dalmat); Coatepeque: 2mi W 
Coatepeque (D.H.Janzen); ElProgreso: 4.9mi SW 
Sanarate, 780m (D.H.Jan/en); Escuintla: 1.7mi S 
Escuintla, 370m [on CA-2] (D.H.Janzen); 12.6mi 
NE Escuintla, rd. to Cd. Guatemala, 1120m 
(D.H.Janzen); 15km E Escuintla [on CA-9] 
(D.H.Janzen); 3mi N Escuintla [on CA-9] 
(D.H.Janzen); 3mi S Escuintla [on CA-9] 
(D.H.Janzen); 43km S Cd. Guatemala [=15km E 
Escuintla] (D.H.Janzen); 6.8mi S Escuintla, 280m 
[on CA-2] (D.H.Janzen); 8.3mi N Escuintla [on 
CA-9] (D.H.Janzen); 9. 2mi N Escuintla, 900m [on 
CA-9] (D.H.Janzen); Escuintla (W.M.Wheeler); 
Pantaleon (Champion); Guatemala: 16.2mi NE 
Cd.Guatemala (D.H.Janzen); 19kmS Cd.Guatemala 
[on CA-9] (D.H.Janzen); 20mi SE Cd.Guatemala, 
1060m [on CA-1] (D.H.Janzen); 6.2mi NE 
Cd.Guatemala, 700m (D.H.Janzen); 7.9mi S Cd. 
Guatemala, 1360m [on CA-9] (D.H.Janzen); 8. Imi 
NE Cd. Guatemala, 850m (D.H.Janzen); Cd. Gua- 
temala (Champion); Cd. Guatemala, 980m 
(D.H.Janzen); Escuintla-Cd.Guatemala [=19km S 
Cd. Guatemala] (D.H.Janzen); Huehuetenango: 
12.4mi SE Mex. border at Cd. Cuauhtemoc 
(D.H.Janzen); 12.5mi SE Mex.border at Cd. 
Cuauhtemoc (D.H.Janzen); 37.6mi NW 
Huehuetenango, 900m (D.H.Janzen); 7. Imi SE 
Mex.border at Cd. Cuauhtemoc (D.H.Janzen); 9.3mi 
SE Mex.border at Cd. Cuauhtemoc (D.H.Janzen); 
Izabal: l.lmi NE Quirigua, 120m (D.H.Janzen); 
2. Imi SW Morales, 50m (D.H.Janzen); Lago Izabal, 
1km NE El Estor [= 1.5km NE El Estor] 
(D.H.Janzen); Los Amates (Kellerman); 
Murciellago (D.H.Janzen); Quirigua 
(W.M.Wheeler); Jutiapa: 6.7mi N San Cristobal, 
280m (D.H.Janzen); 6.9mi N San Cristobal, 290m 
(D.H.Janzen); 9miSW Jutiapa, 950m (D.H.Janzen); 
Peten: 70km NW Tikal (W.R.Tschinkel); Tikal 
(T.H.Hubbell; N.L.H.Krauss; W.R.Tschinkel); 
Quezaltenango: 7.2mi NE San Felipe, on 

Retalhuleu-QuezaltenangoRd. (D.H.Janzen); 7.5mi 
NE San Felipe, on Retalhuleu-Quezaltenango Rd. 
(D.H.Janzen); Retalhuleu: 1.3mi E Champerico 
(D.H.Janzen); 2mi NE Champerico (D.H.Janzen); 
5mi W Retalhuleu (D.H.Janzen); 5mi W Retalhuleu, 
Hwy. CA-2, at Rio Nil (D.H.Janzen); Champerico 
(Baker; F.Knab); Puenta Samala, 3.8mi NE San 
Felipe (D.H.Janzen); Retalhuleu (Stoll); SantaRosa: 
25mi SE Escuintla, 200m [on CA-2] (D.H.Janzen); 
Solola: "Pacific slope", 3000ft. (c.u.); 
Suchitepequez: Patulul (W.M.Wheeler); Zacapa: 
lOmi SW El Lobo, 170m [on CA-9] [=9.2mi NE 
Piedras de Afilar] (D.H.Janzen); 2.6mi SW El 
Lobo, 100m [on CA-9] [=16.6mi NE Piedras de 
Afilar] (D.H.Janzen); 8. Imi SWLos Amates, 160m 
[on CA-9] [=8.0mi NE El Lobo] (D.H.Janzen); 
8.2mi NE Piedras de Afilar, 160m [on CA-9] 
[=12.2mi NE Rio Hondo] (D.H.Janzen); 
dept. unknown: "Guatemala" (Beccari); Concepcion, 
1400ft. (C.N.Ainslie); Mimosa, "Cocepcion" 
[Concepcion] (C.N.Ainslie). 

HONDURAS Atldntida: Tela (quarantine New 
Orleans, U.S.A.) (T.J.Baker); Colon: Puerto Castilla 
(J.Bequaert); Comayagua: "Comayaena" (S. 
Passoa); 1 1.7miS San Antonio, 830m (D.H.Janzen); 
1 5.7mi N Siguatepeque, 530m (D.H.Janzen); Minas 
de Oro (J.B.Edwards); Copdn: 10.4mi S Sta. Rosa 
de Copan, 980m (D.H.Janzen); 1 1.9mi S Sta. Rosa 
de Copan, 1130m (D.H.Janzen); 17.3mi N Sta. 
Rosa de Copan, 780m (D.H.Janzen); Cortes: 24.6mi 
SW San Pedro Sula, 240m (D.H.Janzen); 6.8mi S 
San Pedro Sula, 480m [=20.9mi SW Quimistan] 
(D.H.Janzen); San Pedro Sula (S.C.Bruner; 
W.M.Mann); Ocotepeque: 4.4mi E [Nueva] 
Ocotepeque, 13 10m (D.H.Janzen); Santa Barbara: 
7.3mi E Quimistan (D.H.Janzen); 13.7mi SW 
Quimistan, 320m (D.H.Janzen); Yoro: Coyoles, W 
of Olanchito (Echternacht); dept.unknown: "Hon- 
duras" (Bates). 

MEXICO Camp.: 0. Imi S Tenabo (D.H.Janzen); 
O.Smi E Campeche (D.H.Janzen); 10.6mi E 
Campeche (D.H.Janzen) ; 20mi E Campeche, 
Hwy. 1 80 (D.H.Janzen); 29mi E & 12mi S Campeche 
(Ruinas Edzna)(D.H.Janzen); 48mi NE Puerto Real 
(Isla Aguada), Hwy. 180 (D.H.Janzen); Ruinas 
Edzna (U.Kansas Mex.Exped.); Chis.: 10 mi NE 
[NW?] Tapachula [on Hwy. 200?] (D.H.Janzen); 



10.8mi S Pichucalco (D.H.Janzen); llkm SE 
Pichucalco, 400m (P.S.Ward); 11 mi E Arriaga 
(D.H.Janzen); 1km WSW Palenque, 80m 
(P.S.Ward); 26km E Cintalpa (W.MacKay); 2mi S 
Pichucalco (D.H.Janzen); 32mi W [San] Cristobal 
de las Casas, Hwy.190 (D.H.Janzen); 3km ENE 
Chiapa de Corzo, 500m (P.S.Ward); 3mi N Soyalo 
[on Hwy.195] (D.H.Janzen); 4mi NW Ocosingo 
(R.C.Bechtel & E.I.Schlinger; R.F.Smith); 4mi S 
Simojovel(R.C.Bechtel & E.I.Schlinger; 
E.I.Schlinger); 56.9mi NE [NW?] Tapachula [on 
Hwy.200?] (D.H.Janzen); 5mi SE Tapilula [on 
Hwy.195] (D.H.Janzen); 6.9mi N Tapilula 
(D.H.Janzen); 7mi SW Teapa [on Hwy.195] 
(D.H.Janzen); 8.5mi S La Trinitaria, 1160m 
(U.Kansas Mex.Exped.); 8.5mi S La Trinitaria, 
Hwy.190 (D.H.Janzen); 8mi W Las Cruces, 
Hwy.190, 660m (D.H.Janzen); 96km S Tuxtla 
Gutierrez, 732m (D.E. & J.A.Breedlove); 
Acapetahua Las Bugamvillas (F.Diaz); Arriaga 
(D.H.Janzen); Cd. Cuauhtemoc (D.H.Janzen); 
Chicoasen (G.N.Collins); El Real (Goodnight & 
Stannard); Ixtacomitan (R.Andrews); Llano Grande 
(G.N.Collins); Palenque (c.u.); Pichucalco 
(G.N.Collins); Rio Huixtla, Huixtla (J.G.Pereira); 
Ruinas Palenque (E.M.Fisher); San Sebastian [near 
Tuxtla Gutierrez; see Safford 1922:393] 
(G.N.Collins); Santo Domingo, 15mi SE [SW?] 
Simojovel (R.F.Smith); Tapilula (D.H.Janzen); 
Tonala, 40m (D.H.Janzen); Tonola [prob.=Tonala] 
(A.Petrunkewitch); Tuxtla Gutierrez 
(N.L.H.Krauss; W.P.Stoutamize); Yaxoquintela 
(J.E.Rawlins); Yerba Santa (G.N.Collins); 
Gro.:10mi NE Acapulco (D.H.Janzen); 15.8mi S 
Chilpancingo (D.H.Janzen); 18mi S Chilpancingo 
(F.D.Parker;F.D.Parker & L.A.Stange); 25.4mi S 
Chilpancingo (D.H.Janzen); 55mi N Acapulco, 
Hwy.95 (Cornell Univ.Mex.Field Party; c.u.); 
57.8mi S Chilpancingo (D.H.Janzen); 59.9mi N 
Acapulco (D.H.Janzen); 62.4mi N Acapulco 
(D.H.Janzen); 74km N Acapulco (W.MacKay); 
Acapulco (L.J.Lipovsky); Revolcadero 
(N.L.H.Krauss); San Geronimo de Juarez (W.von 
Hagen); Hgo.: 2km W Orizatlan, 245m 
(W.MacKay); Mor.:15miSCuernavaca (E.S.Ross; 
W.S.Ross); Cuernavaca (W.M.Wheeler); Oax.: 
1 1.4-17.0mi W Tehuantepec (D.H.Janzen); Imi W 
Temascal (D.H.Janzen); 22.2mi N Puerto 

Escondido, 700m (D.H.Janzen); 25mi W 
Tehuantepec (D.H.Janzen); 3.2miNE Tehuantepec 
(D.H.Janzen); 42km N San Pedro Pochutla, 850m 
(W.MacKay); 44mi W Tehuantepec (E.E.Gilbert 
& C.D.MacNeil); 5mi E Temascal (D.H.Janzen); 
9.6km E Santiago Astata, 1 Om (W.MacKay); Bahias 
de Huatulco (W.MacKay); Pinotepa Nacional 
(S.W.T.Batra); Salina Cruz (D.H.Janzen); 
Tehuantepec (F.Knab; W.P.Stoutamize); Temascal 
(H.V.Daly; D.H.Janzen); Temascal, 25m 
(D.H.Janzen);Tuxtepec(J.CamelaG.; W.M.Mann); 
Valle Nacional (G.V.Halffter); Q.Roo: 12.2mi S 
Peto, Q.Roo- Yucatan border (D.H.Janzen); 16.9mi 
W Cd. Chetumal, rd. to Peto (D.H.Janzen); 22.5mi 
S Felipe Carillo Puerto (D.H.Janzen); 6.4mi E 
Polyuc (D.H.Janzen); 7mi W Felipe Carillo Puerto 
(D.H.Janzen); 8. Imi S Felipe Carillo Puerto 
(D.H.Janzen); 8mi S Felipe Carillo Puerto 
(D.H.Janzen); Sian Ka'an (A.Dejean); Sian Ka'an 
Reserve, nr. Felipe Carillo Puerto (A.Dejean); 
Vallarta (A.Dejean); S.L.P. : 27mi N Tamazunchale 
(D.H.Janzen); 40-50mi NW Cd. del Maiz 
(W.S.Ross); 4miN Valles, 300ft. (W.S.Creighton); 
Cd. Valles (D.H.Janzen); El Bonito, 7mi S Cd. 
Valles, 300ft. (P.H. & M.Arnaud); El Salto 
(A.Mintzer; c.u.); Huichihuayan (L.J.Lipovsky); 
Rio Amahac, Tamazunchale, 300ft. (W. S. 
Creighton); Tamazunchale (D. H. Janzen; W. S. 
Ross); locality not specified, prob. Tanquian [see 
Safford 1923:390] (Safford); Tab. : 0.6mi S Paraiso 
onrd. to Cardenas (D.H.Janzen); 0.9mi S Chontalpa 
(D.H.Janzen); 12.8mi S Chontalpa (D.H.Janzen); 
2. Imi E Frontera (D.H.Janzen); 3 mi W Cardenas 
(D.H.Janzen); 30.2mi W Cd. El Carmen 
(D.H.Janzen); 37.8mi E Coatzacoalcos, Hwy.180 
(D.H.Janzen); 6.6mi S Chontalpa (D.H.Janzen); 
Chontalpa, 26mi S Cardenas (D.H.Janzen); 
Cardenas (D.H.Janzen); Teapa (J.C. & D.Pallister; 
H.H.Smith; W.P.Stoutamize); Tamps.: 22.7mi S 
Cd. Victoria (D.H.Janzen); 41mi S Cd. Victoria 
(C.W.Obrien); 50mi N Valles (G.E.Bohart); 5mi N 
Cd. Mante (A.Mintzer); 7km WSW El Encino, 
140m (P.S.Ward); Antiguo Morelos (c.u.); Cd. 
Madero (F.Infante M.); Ciudad Mante (N.E. & 
M.A.Evans; N.L.H.Krauss); El Limon (H.E.Evans); 
Forlon (L.J.Lipovsky); Gonzales (c.u.); Llera 
(W.E.LaBerge); Mesa de Llera (A.Mintzer); N of 
Antiguo Morelos (A.Mintzer); Rio Guayalejo at 

VOLUME 2, NUMBER 1 , 1993 


Hwy.85 (A.S.Menke&L.A.Stange); S of Cd. Mante 
(A.Mintzer); Tampico (Brakhoven; D.L.Crawford; 
H.Jourdan; N.L.H.Krauss; Locke; E. Palmer; 
E.A.Schwarz; W.P.Stephen; c.u.); Tampico, dunes 
at Cd. Madero (D.H.Janzen); Xicotencatl 
(H.C.Millender); Ver.: "N.M.,Vera Cruz" 
(Townsend); "Vera Cruz" (G.Seurat; H.H.Smith); 
lOmi W Veracruz (G.E.Bohart); 14km ENE La 
Tinaja, 50m (P.S.Ward); 15mi W Veracruz 
(U.Kansas Mex.Exped.); 16km E Cuilahuac 
[=Cuitlahuac] (W.MacKay); 24.9miNW Acayucan 
(D.H.Janzen); 28km N Cardel, Morro de la Mancha 
(V.Rico-Gray); 30mi S Acayucan (F.D.Parker); 
3mi N Sayula (R.C.Bechtel; R.C.Bechtel & 
E.I.Schlinger); 4mi NE Minatitlan (R.C.Bechtel & 
E.I.Schlinger);4miNWRinconada Antigua, 1350ft. 
(U.KansasMex.Exped.); 4mi W Puente Nacional, 
900ft. (U.Kansas Mex.Exped.); 6.5km N Tierra 
Blanca, 50m (W.MacKay); 7mi S Cardel, 600ft. 
(c.u.); 9km NNW Sontecomapan, 20m (P.S.Ward); 
Boca del Rio (U.Kansas Mex.Exped.); Buen Pais 
(R.C.Bechtel & E.I.Schlinger); Camaron 
(E.Skwarra); Cordoba (F.Knab; R.R.Snelling; c.u.); 
Cotaxtla Exp. Sta., Cotaxtla (D.H.Janzen); Est. 
Biol. Los Tuxtlas (H.A.Hespenheide); Est. Biol. 
"Los Tuxtlas", nr. San Andres Tuxtla (G.Ibarra 
M.); Fortin (c.u.); Jalapa (Rangel; W.M.Wheeler; 
c.u.); Jalapilla, mun. Jilotepec (G.Aleman); Los 
Cocos (A.Petrunkewitch); Los Tuxtlas, 10km NNW 
Sontecomapan, 200m (P.S.Ward); Mirador 
(E.Skwarra); Mocambo (D.H.Janzen); Orizaba 
(c.u.); Palma Sola (Halffter & Reyes); Panuco 
(F.Parker & D.Miller); Playa Azul, Catemaco 
(W.P.Stoutamize); Pueblo Nuevo, nr. Tezonapa 
(Cornell Univ. Mex. Field Party); Remutadero 
(E.Skwarra); Santa Lucrecia [=Jesus Carranza] 
(F.Knab; P.Knab); Tamarindo (E.Skwarra); Tamos 
(F.C.Bishop); Tinajas [presumably La Tinaja, on 
Hwy.150] (F.D.Parker & L.A.Stange); Tlacocintla 
(E.Skwarra); Veracruz (G.E.Bohart; N.L.H.Krauss; 
E.Skwarra; L.A.Stange); Yuc.: 14.8mi S Ticul, 
"Hwy.180" [prob.Hwy.261] (D.H.Janzen); 8mi E 
Merida (rd. to Pto. Juarez) (D.H.Janzen); Merida 
(D.H.Janzen; N.L.H.Krauss); Merida (S margin of 
town) (D.H.Janzen); Tekax, 33mi W Peto 
(D.H.Janzen); Temax (Gaumer); state unknown: 

Pseudomyrmex flavicornis (F. Smith 1877) 
(Figs. 16, 25, 63, 69) 

Pseudomyrma flavicornis F. Smith 1877:67. Lec- 
totype worker,Nicaragua (BMNH) [Examined]. 

Pseudomyrma belli Emery 1890:63. Syntype work- 
ers, Alajuela, Costa Rica (BMNH, MCSN) [Ex- 
amined] [Synonymy by Ward 1989:438]. 

Pseudomyrma belli var. obnubila Menozzi 
1927a:273. Syntype worker, San Jose, Costa 
Rica (H. Schmidt) (NHMB) [Examined] [Syn- 
onymy by Ward 1989:438]. 

Pseudomyrma belli subsp. fellosa Wheeler 
1942:160. Syntype workers, Nicaragua (W. 
Fluck); Granada, Nicaragua (C. F. Baker) 
(AMNH, LACM, MCZC) [Examined] [Syn- 
onymy by Ward 1989:439]. 
Pseudomyrmex flavicornis (F. Smith); Kempf 

Worker measurements (n = 29). HL 1 .06- 1 .42, 
HW 0.99-1.21, MFC 0.075-0.114, CI 0.83-0.94, 
REL 0.39-0.45, REL2 0.45-0.51, OOI 1.28-2.71, 
VI 0.59-0.73, FCI 0.068-0.098, SI 0.40-0.46, SI2 
0.82-0.97, NI 0.61-0.68, PLI 0.57-0.67, PWI 0.60- 
0.72, PPWI 1.36-1.80. 

Worker diagnosis. Similar to P. ferrugineus 
(q.v.) except as follows. Larger, with shorter eyes, 
on average (Figs. 16,50). Head densely punctulate, 
opaque; overlying rugulo-punctate sculpture on 
propodeum tending to be better developed than in 
P. ferrugineus. Pilosity and pubescence denser on 
average. Head black, gaster and postpetiole dark 
brown to black, mesosoma and petiole varying 
from black to a contrasting lighter brown or red- 
dish-brown; mandibles, scapes, fronto-clypeal com- 
plex, and apices of legs brown. 

Comments. Key traits of this species are the 
laterally rounded median clypeal lobe, large size 
(worker HW > 0.98; queen HW 1.12-1.19, n=13), 
broad opaque head (worker CI > 0.82; queen CI 
0.73-0.76) and dark color. P. flavicornis is one of 
three species in the P. ferrugineus group whose 
workers and queens have a black or very dark 
brown body (mesosoma sometimes contrastingly 
lighter). The other two, P. mixtecusandP. veneficus, 
are allopatric to P. flavicornis and smaller in size; 



other distinguishing features are mentioned in the 
key and discussed under those species. A tendency 
towards lighter coloration of the mesosoma in north- 
ern populations ofP.flavicornis sometimes makes 
it difficult to distinguish this species from sympa- 
tric dark-colored P. ferrugineus. Even the darkest 
workers and queens of the latter species are, how- 
ever, smaller (an average difference in workers, 
almost absolute in P. ferrugineus queens which 
have HW 0.96- 1 . 1 2 (n = 37)) with longer eyes (Fig. 
50) and shorter scapes for a given relative head 
breadth (Fig. 51); and they show some reflectance 
of light on the upper third of the head between the 
ocelli and compound eye in contrast to the more or 
less opaque-headed P. flavicornis. In addition, P. 
ferrugineus queens have more elongate heads (CI 
0.68-0.73) than those of P. flavicornis. 

Distribution and biology. This is a monogy- 
nous species ranging from Guatemala to Costa Rica 
(Fig. 69), which inhabits Acacia collinsii and, less 
frequently, A. cornigera and A. hindsii. It was one 
of the first acacia-ants to be brought to the attention 
of naturalists, thanks to an early account of its 
biology by Thomas Belt (1874) (under the name 
Pseudomyrma bicolor). In the more recent litera- 
ture P. flavicornis has usually been referred to as 
"P. belli", but note that there is not a perfect 
correspondence in name usage (Table 1). 

Material examined (AMNH, ANSP, BMNH, 

COSTA RICA Alajuela: Alajuela (A.Alfaro); 
Atenas (A.Alfaro); Ojo de Agua (A.Alfaro); Tacares 
(A.Alfaro); Turrucares (A.Alfaro); Guanacaste: 
1.4mi N La Cruz, 200m (D.HJanzen); 10.7mi NW 
Liberia (D.HJanzen); 1km S Canas (D.HJanzen); 
2mi E Playa Coco (D.HJanzen); 2mi SE Canas 
[=2mi S Canas] (D.HJanzen); 4km S 
Canas(D.HJanzen); 5km S Liberia (D.HJanzen); 
6mi E, 6mi S Canas (D.HJanzen); 6mi W Liberia 
(D.HJanzen); 7km N Canas (D.HJanzen); Bahia 
del Coco (A.Alfaro); Ballena, Rio Tempisque 
(A.Alfaro); El Coco (R J.Hampton); FincaTaboga, 
6mi S, 6mi W Canas (D.HJanzen); Hda. LaPacifica, 
5km NW Canas (E.R.Heithaus); Hda. La Pacifica, 
nr. Canas, 50m (P.S.Ward); La Cueva, 12km N 
Liberia (D.HJanzen); Liberia (A.Alfaro; 

M.G.Naumann); Palo Verde (D.E.Gill; 
H.A.Hespenheide; D.HJanzen; D.Whitacre); Palo 
Verde, 50m (D.M.Olson); Palo Verde, <100m 
(J.Longino); Rio Corobici, nr.Canas (R.M.Bohart); 
Santa Cruz (P.P.Calvert); Santa Rosa Natl. Pk. 
(F Joyce); Santa Rosa Natl. Pk., 300m (J.Longino; 
P.S.Ward); Santa Rosa Natl. Pk., 5m (P.S.Ward); 
Santa Rosa Natl. Pk., <5m (P.S.Ward); Tempisque 
(A.Alfaro); Heredia: Lagunilla (C.H.Ballow); 
Puntarenas: 1km NE Tarcoles, 20m (P.S.Ward); 
4km E Tivives, 5m (L.S.Farley); Barranca,near 
Puntarenas (A.Alfaro); San Jose: Bebedero 
(A.Alfaro); Rio Oro (D.HJanzen); San Jose 
(Nauck;H.Schmidt); Villa Colon (A.Alfaro); Villa 
Colon, 600-700m (J.Longino); prov. unknown: 
"Costa Rica"(c.u.); Ciruela(J.F.Tristan). 

EL SALVADOR Ahuachapan: 7.8mi S 
Hachadura, 50m (D.HJanzen); Chalatenango: 
5 .4mi N La Palma, 850m (D .H Janzen) ; La Libertad: 
2.6miS Santa Tecla,1010m[=11.8miNLaLibertad] 
(D.HJanzen); 2mi E La Libertad (D.HJanzen); La 
Libertad (E.S.Ross); Quezaltepeque (D.Cavagnaro 
& M.E.Irwin); La Union: 7. Imi W Amatillo, 190m 
(D.HJanzen); Lapaz: 11.6mi W Zacatecoluca, Om 
(D.HJanzen); San Miguel: 0.4mi W San Miguel 
(D.H Janzen); betw. La Union & San Miguel, 1 10m 
(D.HJanzen); San Salvador: San Salvador 
(O.L.Cartwright; N.L.H.Krauss); Sonsonate: 
34.4mi W La Libertad (D.HJanzen); 6.6mi S 
Sonsonate [=43. 6mi W La Libertad] (D.HJanzen); 
Usulutan: E slope Cerro Verde, 3800ft. 
(D.Q.Cavagnaro & M.E.Irwin); dept. unknown: Los 
Chorros (D.Q.Cavagnaro & M.E.Irwin); Los 
Chorros Natl. Pk. (M.E.Irwin). 

GUATEMALA Escuintla: 12.6miNEEscuintla, 
rd. to Cd. Guatemala, 1120m (D.HJanzen); 15km 
E Escuintla [on CA-9] (D.HJanzen); 43km S Cd. 
Guatemala [=15km E Escuintla] (D.HJanzen); 
Guatemala: 19km S Cd. Guatemala [on CA-9] 
(D.HJanzen); 7.9mi S Cd. Guatemala [on CA-9] 
(D.HJanzen); Amatitlan (Bates); Escuintla- 
Cd. Guatemala [=19km S Cd. Guatemala] 
(D.HJanzen); Lake Amatitlan (c.u.);Jutiapa:47mi 
S Escuintla, 250m [=47mi SE Escuintla] 
(D.HJanzen); 7.7mi E Jutiapa, Hwy.l, 900m 
(D.HJanzen); 9.7mi E Jutiapa, 750m ( San 
Cristobal) [=9.3miNE Jutiapa] (D.HJanzen); Santa 
Rosa: 12.2mi W Taxisco (D.HJanzen); 3.8mi S 

VOLUME 2, NUMBER 1, 1993 


Guazacapan (D.H.Janzen); Guazacapan 
(R.H.Painter); Zacapa: lOmi SW El Lobo, 170m 
[on CA-9] [=9.2mi NE Piedras de Afilar] 
(D.H.Janzen); 2.6rai SW Rio Hondo, 200m [on 
CA-9] (D.H.Janzen); 22.3mi SW Quirigua [on CA- 
9] (D.H.Janzen); 22.3mi SW Quirigua [on CA-9] 
(D.H.Janzen); 8.2mi NE Piedras de Afilar, 160m 
[on CA-9] [=12.2miNE Rio Hondo] (D.H.Janzen); 
km 142 on Guatemala-Pto. Barrios Rd. nr. Los 
Amates (D.H.Janzen). 

HONDURAS Choluteca: 19mi NE Choluteca 
(D.H.Janzen); 3.6mi W Choluteca, 200m 
(D.H.Janzen); 4.5mi W Choluteca (D.H.Janzen); 
Colon: Puerto Castilla (J.Bequaert); Valle: 4.6mi E 
Jicaro Galan, 1 90m (D .H. Janzen) ; La Union, 28 .4mi 
E El Amatillo (frontera) (D.H.Janzen). 

NICARAGUA Chontales: no specific locality 
(T.Beit); Esteli: 2mi N Condega, 500m 
(D.H.Janzen); Granada: 2.2mi W Nandaime 
(D.H.Janzen); 2mi N Nandaime, 160m 
(D.H.Janzen); Granada (C.F.Baker); Leon: 28.1mi 
SE Leon (D.H.Janzen); Managua: S.lmi E San 
Benito (D.H.Janzen); 8.8mi N Tipitapa 
(D.H.Janzen); 9.9miNEMasachapa,Hwy.8, 180m 
(D.H.Janzen); 9mi N Tipitapa, 50m (D.H.Janzen); 
Matagalpa: 15.8mi NW Sebaco [=15.8mi W 
Sebaco] (D.H.Janzen); 2.6miNDario (D.H.Janzen); 
4.1mi S Matagalpa, 650m (D.H.Janzen); 4.5mi SE 
Dario (D.H.Janzen); Rivas: Imi N San Juan del Sur 
(D.H.Janzen); Imi NW Penas Blancas [=lmi N 
Penas Blancas] (D.H.Janzen); 20.5mi NW Penas 
Blancas (D.H.Janzen); 4.4miSELa Virgen [=4.4mi 
S La Virgen] (D.H.Janzen); Isla Ometepe (F.Joyce); 
La Virgen [on Hwy.l] (D.H.Janzen); San Juan del 
Sur, 10m (D.H.Janzen); Zelaya: Wounta Hanlover 
(Fluck); dept.unknown: "Nicaragua" (W.Fluck; 

Pseudomyrmex janzeni Ward, sp. 
(Figs. 19, 29, 64, 70) 


Holotype worker. MEXICO, Nayarit: 60 mi. 
SE Acaponeta, Hwy. 15, 15.ix.1963, D. H. Janzen 
(LACM). HW 1 .00, HL 1 .08, EL 0.5 1 , PL 0.55, PH 

Paratypes. Same data as holotype: series of 
166 workers, 62 queens and 45 males (AMNH, 

tional non-type material is listed below. 

Worker measurements (n = 12). HL 1 .00- 1.18, 
HW 0.93-1.03, MFC 0.063-0.096, CI 0.88-0.94, 
REL 0.45-0.47, REL2 0.49-0.52, OOI 1.45-2.29, 
VI 0.58-0.68, FCI 0.068-0.098, SI 0.42-0.45, SI2 
0.84-0.91, NI 0.62-0.69, PLI 0.59-0.71, PWI 0.63- 
0.73, PPWI 1.37-1.73. 

Worker diagnosis. Very similar to P. 
ferrugineus (q.v.) except as follows. Size smaller, 
on average. In lateral view mesonotum less steeply 
inclined; basal and declivitous faces of propodeum 
forming a less obtuse angle (compare Figs. 27 and 
29). Petiole shorter and higher, on average (Fig. 
48). Weak rugulo-punctate sculpture on propodeum 
even less evident than in P. ferrugineus. Pubes- 
cence denser, becoming decumbent to suberect on 
parts of body, most notably the gula (Fig. 19). Head 
and mesosoma rather light orange-brown, gaster 
the same or a slightly darker brown. 

Comments. Within the P. ferrugineus group 
P. janzeni can be characterized by its relatively 
small size (worker and queen HW < 1.04), broad 
head (worker CI > 0.86), laterally rounded median 
clypeal lobe, and uniform orange-brown color. P. 
janzeni is evidently closely related to P. ferrugineus 
(as surmised by Janzen 1973); all of the metric 
measurements and indices of these two species 
overlap, although there is a tendency for P. janzeni 
workers to have shorter, higher petioles (Fig. 48). 
Workers and queens of P. janzeni are perhaps best 
distinguished from those of P. ferrugineus by the 
combination of lighter orange-brown color, suberect 
gular pubescence (best seen in a backlit lateral view 
of the head), and the flatter profile of the worker 
mesosoma (see description above and Fig. 29). 
While some individuals of the highly variable P. 
ferrugineus approach these conditions there is no 
indication of a convergence towards this morphol- 
ogy in western Mexico (Guerrero) where popula- 
tions of P. ferrugineus come closest to those of P. 

Distribution and biology. First recognized by 
Janzen (1967a, 1969, 1973) as a distinct but 
undescribed species, P. janzeni is confined to a 
limited area in western Mexico (Fig. 70) where it is 
sympatric with the much darker colored and com- 



moner P. veneficus. Colonies occupy Acacia hindsii 
and are polygynous; additional details of the life 
history can be found in Janzen's (1973) paper on 
polygynous acacia-ants. 

Material examined. Type material listed above, 
plus the following (LACM, MCZC, PSWC, UCRC, 

MEXICO Jal. : Puerto Vallarta (J. A.Comstock) ; 
Nay.: 14.5mi E San Bias (D.HJanzen); 2mi E San 
Bias (R.van den Bosch); 31mi N Tepic 
(D.HJanzen); 36mi N Tepic (D.HJanzen); 4mi E 
San Bias (M.Irwin; M.Irwin & E.I.Schlinger; 
EJ.Schlinger); 5mi E San Bias (F.Parker & 
D.Miller); Compostela (c.u.); Rio Palillo, 14mi E 
San Bias (D.HJanzen); Tepic (H.A.Scullen); Sin.: 
20mi E Villa Union (E.I.Schlinger). 

Pseudomyrmex mixtecus Ward, sp. nov. 
(Figs. 15, 26, 55, 61, 69) 

Holotype worker. MEXICO, Guerrero: 25.4 
mi. S. Chilpancingo, 10.viii.1966, D. H. Janzen 
#M0088 10966 (LACM). HW 0.97, HL 1.07, EL 
0.48, PL 0.55, PH 0.35. 

Paratypes. Same data as holotype, and three 
other accession numbers (M0078 10966, 
M0098 10966, MO 108 10966) with same locality, 
date, and collector: series of 43 workers, 34 queens 
and 17 males (AMNH, BMNH, CASC, EBCC, 
UCDC, USNM). Additional non-type material is 
listed below. 

Worker measurements (n= 13). HLO.94-1.19, 
HW 0.89-1.03, MFC 0.054-0.073, CI 0.86-0.95, 
REL 0.42-0.47, REL2 0.46-0.52 OOI 1 .22-2.28, VI 
0.97, NI 0.60-0.65, PLI 0.60-0.68, PWI 0.60-0.68, 
PPWI 1.40-1.73. 

Worker diagnosis. Similar to P. ferrugineus 
(q.v.) except as follows. Size smaller (HW < 1.04, 
LHT < 0.90), head broad (CI > 0.85); frontal 
carinae separated by about basal scape width or less 
(FCI2 0.45-0.54). Basal and declivitous faces of 
propodeum forming a less obtuse angle in profile 
than typical for P. ferrugineus (compare Figs. 26 
and 27). Head densely punctulate, opaque. Stand- 
ing pilosity rather common, usually some setae 
exceeding 0.12 mm and 0.20 mm in length on 

mesosoma dorsum and petiole, respectively. Pu- 
bescence dense but appressed. Very dark brown to 
black, appendages lighter. 

Comments. P. mixtecus is distinguished from 
all other species, except P. veneficus and P. 
flavicornis, by its laterally rounded median clypeal 
lobe, broad head, and black (or very dark brown) 
body. It differs from P. veneficus by the fully 
opaque head, absence of conspicuous suberect pu- 
bescence on the petiole, and larger size. P. mixtecus 
is evidently closely related to P. flavicornis but 
averages smaller in size (compare worker HW and 
LHT values), a difference which is absolute in 
queens (queen HW 0.96- 1.01 (n=8), whereas queen 
HW > 1 . 1 1 in P. flavicornis). In addition the petiole 
is relatively longer and higher, for a given head 
width, in both workers and queens of P. mixtecus 
(Figs. 44-47). 

Distribution and biology. P. mixtecus is known 
only from the Mexican states of Guerrero and 
Oaxaca (Fig. 69). Colonies have been collected 
from Acacia hindsii and A. collinsii, but little more 
has been recorded about their biology. Janzen's 
field notes indicate that this species is monogynous. 

Material examined. Type material listed above, 
plus the following (CUIC, LACM, MCZC, MZSP, 

MEXICO Gro.: lOmi NE Acapulco 
(D.HJanzen); 29.6mi N Acapulco, 1400ft. 
(D.HJanzen); 30mi N Acapulco, Hwy.95 (Cornell 
Univ. Mex. Field Party); 57.8mi S Chilpancingo, 
Hwy.95 (D.HJanzen); 74km N Acapulco 
(W.MacKay); Acapulco (Baker; F.Knab; 
N.L.H.Krauss; LJ.Lipovsky); Puerto Marques 
(N.L.H.Krauss); San Geronimo de Juarez (W.von 
Hagen); Oax.:l 1.4-17.0mi W Tehuantepec 
(D.HJanzen); 13.8mi W Tehuantepec, 1500ft. 
(D.HJanzen); 19km N San Pedro Pochutla, 200m 
(W.MacKay); 6.0mi E Niltepec, Hwy.190, 100m 

Pseudomyrmex nigrocinctus (Emery 1 890) 
(Figs. 13, 22, 56, 72) 

Pseudomyrmanigrocincta Emery 1890:64. Syntype 
workers, queens, males, Alajuela, Costa Rica 
(A. Alfaro) (BMNH, MCSN, MCZC, MHNG) 
[Examined]. One syntype worker from MCSN 

VOLUME 2, NUMBER 1, 1993 


here designated LECTOTYPE. 
Pseudomyrma alfariForel 1906:228. Twosyntype 

workers, Tivives, embouchure de Jesus-Maria, 

Costa Rica (A. Alfaro) (MHNG) [Examined]. 

One syntype here designated LECTOTYPE. 

Syn. nov. 
Pseudomyrma nigrocinta var. bicincta Santschi 

1922:347. Syntype workers, Costa Rica 

(MHNG, NHMB) [Examined]. One syntype 

from NHMB here designated LECTOTYPE. 

Syn. nov. 
Pseudomyrma peltataMenozzi 1927a:273. Three 

syntype workers, SanJose, Costa Rica (H. 

Schmidt) (NHMB) [Examined]. Syn. nov. 
Pseudomyrmex nigrocincta [sic] (Emery); Janzen 

Pseudomyrmex nigrocinctus (Emery); Kempf, 


Worker measurements (n = 21). HL 0.89- 1.08, 
HW 0.74-0.85, MFC 0.035-0.051, CI 0.75-0.84, 
REL 0.40-0.45, REL2 0.51-0.56, OOI 1.39-2.76, 
VI 0.62-0.78, FCI 0.044-0.065, SI 0.44-0.48, SI2 
0.81-0.89, NI 0.58-0.64, PLI 0.59-0.68, PWI 0.49- 
0.61, PPWI 1.10- 1.30. 

Worker diagnosis. Small species with elon- 
gate head and short eyes (REL 0.45, REL2 0.56, 
EL/LHT 0.61). Palp formula 5,3. Median clypeal 
lobe rather narrow, its surface and anterior margin 
convex. Frontal carinae separated by about basal 
scape width (FCI 0.055). Metanotal groove well 
marked; basal and declivitous faces of propodeum 
subequal (Fig. 22). Petiole short (PLI > 0.57), its 
anterior peduncle broad in dorsal view (PWI3 0.50- 
0.61) and not well differentiated from the node 
(Fig. 22). Petiole lacking expanded posterolateral 
corners. Postpetiole less broad than in most other 
species in the P. ferrugineus group (see PPWI 
values). Head densely punctulate and subopaque, 
becoming sublucid posteriorly where the punctulae 
are separated by shiny interspaces. Mesosoma 
punctulate to (laterally) coriarious-imbricate, 
sublucid, becoming subopaque on the propodeum. 
Standing pilosity moderately common (as in Fig. 
22); pubescence dense and closely appressed. Or- 
ange-brown, often with anterolateral fuscous patches 
on abdominal tergite IV (these form a distinct 

transverse black band in queens). 

Comments. Workers and queens of P. 
nigrocinctus are easily distinguished from all other 
acacia ants, except P. particeps (see below), by 
their small size (HW < 0.86 in both castes), elongate 
head in the worker (worker CI < 0.85), and narrow 
petiole andpostpetiole (worker PWI3 0.50, worker 
PPWI 1 .30, queen PWI2 0.57-0.63). The orange 
color and short eyes are also characteristic. 

Distribution and biology. P. nigrocinctus is 
found from Guatemala to Costa Rica, with most 
records coming from the southern end of its range 
(Fig. 72). Colonies are monogynous, and have 
been collected from Acacia collinsii, A. cornigera 
and A. hindsii. Records from Acacia gentlei and A. 
globulifera (Beulig & Janzen 1969:59) need to be 
confirmed because of possible confusion with P. 
peperi. Janzen' s (1967b) observations on "P. 
nigrocincta" in Mexico refer to P. peperi. On the 
other hand descriptions of the biology and behavior 
of P. nigrocinctus in Costa Rica (Janzen 1973, 
1974, 1975, 1983; Beulig & Janzen 1969) are 
reliably attributed to P. nigrocinctus. 

Material examined (AMNH, ANSP, INBC, 

COSTA RICA Alajuela: Alajuela (A.Alfaro); 
Atenas (A.Alfaro); Cascajal (A.Alfaro); Escobal 
(A.Alfaro); Ojo de Agua (A.Alfaro); Turrucares 
(P.P.Calvert); Guanacaste: 1.4mi N La Cruz 
(D.HJanzen); 10.7mi NW Liberia (D.HJanzen); 
lOmi NW Liberia, 70m (D.HJanzen); lOmi NW 
Liberia, 70m [=10.7mi NW Liberia] (D.HJanzen); 
2mi S Canas (D.HJanzen); 4km N Canas 
(D.HJanzen); 5km S Liberia (D.HJanzen); 7km N 
Canas (D.HJanzen); El Coco (R.J.Hampton); Finca 
Taboga, 6mi S, 6mi W Canas (D.HJanzen); Garita 
(A.Alfaro); Hda. La Pacifica, nr. Canas, 50m 
(P. S. Ward); La Cueva, 12km N Liberia 
(D.HJanzen); Palo Verde (D.E.Gill; D.HJanzen); 
Palo Verde, 50m (D.M.Olson); Santa Cruz 
(P.P.Calvert); Santa Rosa Natl. Pk., 290m 
P.S.Ward); Santa Rosa Natl. Pk., 5m (P.S.Ward); 
Santa Rosa Natl. Pk., <5m (P.S.Ward); Tempisque 
(A.Alfaro); Puntarenas: 2km E Tivives, <5m 
(L.S.Farley); Tivives (A.Alfaro); San Jose: 3.5km 
NE Santiago de Pur (D.HJanzen); San Jose 



(H.Schmidt; c.u.); prov. unknown: "Costa Rica" 

GUATEMALA Zacapa: 2.0mi NE Rio Hondo, 
190m [on CA-9] (D.HJanzen); 22.3mi SW Quirigua 
[on CA-9] (D.HJanzen). 

HONDURAS Choluteca: 7.4miNECholuteca, 
150m (D.HJanzen). 

NICARAGUA Boaco: 11.7mi E San Benito 
(D.HJanzen); Esteli: 13.1mi N San Isidro 
(D.HJanzen); 2.5mi N Condega, 620m 
(D.HJanzen); 6.8mi N San Isidro, 780m 
(D.HJanzen); 7.5mi NW San Isidro, 550m 
(D.HJanzen); Leon: Izapa (J.M.Maes); Madriz: 
3mi W Somoto, 650m (D.HJanzen); Matagalpa: 
15.8mi NW Sebaco (D.HJanzen); 2.6mi N Dario 
(D.HJanzen); 4.5mi SE Dario (D.HJanzen); 4mi S 
Dario, 350m (D.HJanzen); Rivas: 1km W Penas 
Blancas (D.HJanzen); C.R. border, Imi N Penas 
Blancas, <5m [=lmi NW Penas Blancas] 
(D.HJanzen); Isla Ometepe (F Joyce). 

Pseudomyrmex particeps Ward, sp. nov. 

(Figs. 14, 23, 54, 57, 72) 

Holotype worker. COSTA RICA, Puntarenas: 
Rincon, Peninsula Osa, 3.iii.l965, D.H. Janzen#III 
(LACM). HW 0.83, HL 1.10, EL 0.50, PL 0.50, PH 

Paratypes. Same data as holotype: series of 82 
workers, 14 males, one queen (AMNH, BMNH, 
MZSP, PS WC, UCDC, USNM). Additional non- 
type material listed below. 

Worker measurements (n = 12). HL 0.93- 1.10, 
HW 0.77-0.83, MFC 0.037-0.050, CI 0.75-0.84, 
REL 0.44-0.48, REL2 0.55-0.60, OOI 1.47-1.96, 
VI 0.65-0.75, FCI 0.048-0.062, SI 0.45-0.49, SI2 
0.78-0.83, NI 0.53-0.62, PLI 0.58-0.66, PWI 0.55- 
0.60, PPWI 1.03- 1.26. 

Worker diagnosis. Very similar to P. 
nigrocinctus (q.v.) except as follows. Eyes longer 
(REL2 0.55-0.60, EL/LHT 0.59-0.64) (Figs. 14, 
42, 43). Front of head more strongly shining. 
Medium to dark brown; gaster uniformly dark 
brown or black; mandibles, fronto-clypeal com- 
plex, and appendages lighter brown. 

Comments. P. particeps is obviously a very 
close relative of the allopatric P. nigrocinctus, but 

there are consistent differences between the two in 
eye size and color which exceed the limits of 
variation seen throughout the much wider range of 
P. nigrocinctus. Workers in the type series of P. 
particeps also have more elongate heads than those 
of P. nigrocinctus but this distinction is not seen in 
other samples. Differences between queens of the 
two species are more striking with the two known 
queens of P. particeps having more elongate heads 
(CI 0.61, compared with 0.67-0.72 in a sample of 
1 3 P. nigrocinctus queens) and longer metatibiae 
relative to head width (LHT/HW 1.12 versus 
0.97-1.07 in P. nigrocinctus). Additional alates of 
P. particeps are needed to confirm these differ- 
ences and the apparent distinctions in male genita- 
lia (see male key). 

Distribution and biology. P. particeps is a rare 
species known only from the Osa Peninsula and one 
adjacent locality, in Costa Rica (Fig. 72). It appears 
to be associated exclusively with Acacia allenii, a 
forest species (see Janzen, 1974 for more informa- 
tion aboutthehostplant). In contrast, P. nigrocinctus 
is found farther north in more open habitats where 
it typically inhabits Acacia collinsii. The differ- 
ences in worker morphology between P. particeps 
and P. nigrocinctus (darker color and more elon- 
gate head and/or eyes in the former) parallel those 
observed between populations of P. spinicola from 
the same areas (see below under P. spinicola), 
suggesting similar selection pressures associated 
with more forested habitats and partial (P. spinicola) 
or exclusive (P. particeps) occupancy of a different 
Acacia species. 

Material examined. Type material listed above, 
plus the following (JTLC, LACM, PSWC). 

COSTA RICA Puntarenas: 4mi S Rincon 
(D.HJanzen); Bahia Drake, Osa Penin. (F.Joyce); 
Corcovado Natl. Pk., Sirena, 50m (J.T.Longino); 
Rincon (A.R.Moldenke); San Jose: 16.7mi SW San 
Isidro on Hwy.22, 160m (D.HJanzen). 

Pseudomyrmex peperi (Forel 1913) 
(Figs. 12,24,58,71) 

Pseudomyrma peperi Forel 1913:213. Syntype 
workers, Patulul, Guatemala (Peper) (MHNG) 
[Examined]. One syntype here designated 

VOLUME 2, NUMBER 1, 1993 


Pseudomyrma spinicola race convarians Forel 
1913:214. Syntype worker, Patulul, Guatemala 
(Peper) (MHNG) [Examined] [Synonymy by 
Ward 1989:452]. 

Pseudomyrma sabanica [sic] var. saffordiEnzmann 
1945:89. Syntype workers, Yerba Santa, 
Chiapas, Mexico (G. N. Collins) (MCZC) [Ex- 
amined] One syntype here designated LECTO- 
TYPE. [Synonymy by Ward 1989:452]. 

Pseudomyrmex peperi (Forel); Kempf 1972:222. 

Worker measurements (n = 53). HL 0.86- 1.13, 
HW 0.76-0.90, MFC 0.034-0.064, CI 0.76-0.89, 
REL 0.45-0.50, REL2 0.54-0.62, OOI 1.15-2.06, 
VI 0.59-0.79, FCI 0.042-0.071, SI 0.44-0.49, SI2 
0.76-0.88, NI 0.62-0.71, PLI 0.54-0.65, PWI 0.63- 
0.75, PPWI 1.41-1.83. 

Worker diagnosis. Small species (HW < 0.92) 
with moderately elongate head (Fig. 12); anterior 
margin of median clypeal lobe straight or slightly 
produced medially, laterally rounded or subangulate 
(never sharply angulate as in P. spinicola and P. 
satanicus). Palp formula 4,3, rarely 5p4,3. Frontal 
carinae separated by about basal scape width. 
Mesosomal and petiolar profile typically as in Fig. 
24, but in some workers basal and declivitous faces 
of propodeum less well differentiated and/or 
anteroventral tooth of petiole more prominent. 
Petiole and postpetiole broad, the former 
subtriangular in dorsal view with well developed 
posterolateral angles (Fig. 24). Dorsum of head 
obscurely punctulate-coriarious, matte. Remainder 
of body with finely punctulate to punctulate- 
coriarious sculpture, opaque to sublucid; propodeum 
lacking overlying rugulo-punctate sculpture seen 
in P. ferrugineus. Standing pilosity not especially 
abundant, sometimes lacking (worn?) on 
mesonotum. Appressed pubescence abundant but 
very fine. Light to medium brown, rarely dark 
brown, the gaster sometimes darker than the rest of 
body; appendages lighter. 

Comments. P. peperi is recognized by the fea- 
tures mentioned above and in the key. The combi- 
nation of small elongate head, broad posterolaterally 
angulate petiole, and matte head surface is found in 
no other acacia ant workers or queens. 

Distribution and biology. This species has a 
rather wide distribution, from eastern Mexico to 

Nicaragua (Fig. 71). It has been collected from 
Acacia chiapensis, A. collinsii, A. cornigera, A. 
gentlei, A. globulifera and A. hindsii. P. peperi is 
apparently polygynous over much of its range, and 
often occurs sympatrically with the commoner P. 
ferrugineus. Some aspects of its biology in Mexico 
are discussed by Janzen ( 1 967b) under the name "P. 
nigrocincta" . 

Material examined (AMNH, BMNH, CASC, 

BELIZE Belize: 16mi SW Belize, rd. to Cayo 
(D.HJanzen); 5.5mi NW Belize, rd. to Chetumal 
(D.H.Janzen); Cayo: 20km S Augustine, 300m 
(G.D.Alpert); Sanlgnacio (S.E.Schoenig); Corozal: 
15mi S Sta.Elena (Louisville) (D.H.Janzen). 

EL SALVADOR Ahuachapan: 7.8mi S 
Hachadura (D.HJanzen); Chalatenango: 2.5mi N 
Tejutla, rd. to LaPalma, 580m (D.H.Janzen); 4.7mi 
NW La Palma, 880m (D.H.Janzen); 5.5mi SE La 
Palma, 1130m (D.H.Janzen); 7.5mi SE Tejutla, 
320m (D.H.Janzen); La Libertad: 2-4km S 
Quezaltepeque (W.L. Brown); 2mi E La Libertad 
(D.H.Janzen); 5mi N Quezaltepeque (M.E.Irwin); 
7.4miNLa Libertad (D.H.Janzen); Hda. Capolinas, 
5kmNW Quezaltepeque, 450m (M.E.Irwin); 
Quezaltepeque (M.E.Irwin); Santa Tecla [=Nueva 
San Salvador] (P.Berry); La Union: 1 Arm W 
Amatillo, 190m (D.H.Janzen); between La Union 
& San Miguel, 100m [=22.3mi S Sirama] 
(D.H.Janzen); between La Union & Usulatan, 1 50m 
[=2.6mi S Sirama] (D.H. Janzen); Lapaz: 1 1.6mi W 
Zacatecoluca, Om (D.H.Janzen); San Miguel: be- 
tween La Union & San Miguel, 1 10m [=22.3mi E 
Usulutan] (D.H.Janzen); Santa Ana: 5.3mi NW 
Santa Ana, 660m (on Hwy.l) (D.H.Janzen); 
Sonsonate: 24.2mi SE Hachadura (D.H.Janzen); 
4.5mi S Sonsonate (D.H.Janzen); 41.4mi NW La 
Libertad, 10m (D.H.Janzen). 

GUATEMALA A/to Verapaz: San Joaquin, nr. 
San Cristobal Verapaz, 1080m (D.H.Janzen); El 
Progreso: 24.5mi NE Cd. Guatemala [on CA-9] 
(D.H.Janzen); Escuintla: 1.7mi S Escuintla, 370m 
[on CA-2] (D.H.Janzen); 43km S Cd. Guatemala 
[=15km E Escuintla] (D.H.Janzen); Escuintla 
(W.M.Wheeler); San Jose (E.S.Ross; E.I.Schlinger 
& E.S.Ross); Guatemala: 19km S Cd. Guatemala 



[on CA-9] (D.HJanzen); 20mi SE Cd. Guatemala, 
1060m [on CA-1] (D.HJanzen); 7.9mi S Cd. Gua- 
temala, 1360m [onCA-9] (D.HJanzen) ;Escuintla- 
Cd. Guatemala [=19km S Cd. Guatemala] 
(D.HJanzen); Izabal: 9.9mi SW Quirigua 
(D.HJanzen); Lago Izabal, 1.5km NE El Estor 
(D.HJanzen); Quirigua (D.HJanzen; 
W.M.Wheeler); nr. Mariscos (D.HJanzen); Jutiapa: 
11.5ml W Jutiapa, 900m (D.HJanzen); 12.3mi E 
Guazacapan (D.HJanzen); 2.3mi NW Pijiji [=Pijije] 
(D.HJanzen); 23mi E Taxisco (G.F. & S.Hevel); 
3.4mi N San Cristobal, rd. to Jutiapa, 400m 
(D.HJanzen); 47mi SE Escuintla, 250m [=47mi S 
Escuintla] (D.HJanzen); 6.9mi N San Cristobal, 
290m (D.HJanzen); 8.4mi N San Cristobal, 280m 
(D.HJanzen); 9.7mi E Jutiapa, 750m ( San 
Cristobal) [=9.3miNE Jutiapa] (D.HJanzen); Peten: 
70km NW Tikal (W.R.Tschinkel); Tikal 
(D.HJanzen; W.R.Tschinkel);fleta//zw/<?:2miNE 
Champerico (D.HJanzen); 5mi W Retalhuleu 
(D.HJanzen); 5mi W Retalhuleu, Hwy.CA-2, at 
Rio Nil (D.HJanzen); Santa Rosa: 6mi S 
Guazacapan (D.HJanzen); Suchitepequez: Patulul 
(Peper); Zacapa: lOmi SW El Lobo, 170m [on CA- 
9] [=9.2mi NE Piedras de Afilar] (D.HJanzen); 
2.0mi NE Rio Hondo, 190m [on CA-9] 
(D.HJanzen); 2.6mi SW El Lobo, 100m [on CA-9] 
[= 1 6.6mi NE Piedras de Afilar] (D.HJanzen) ; 5 .6mi 
NE Rio Hondo, 250m [on CA-9] (D.HJanzen); 
8.1ml SW Los Amates, 160m [on CA-9] [=8.0mi 
NE El Lobo] (D.HJanzen); 9.7mi NE Piedras de 
Afilar, 150m [on CA-9] [=9.5mi SW El Lobo] 
(D.HJanzen); Zacapa (W.M.Wheeler); km!42 on 
Guatemala-Pto. Barrios Rd. nr. Los Amates 

HONDURAS Choluteca: 19.3mi SW San 
Marcos de Colon, on Hwy.l (D.HJanzen); 19mi 
NE Choluteca (D.HJanzen); 20.4mi SW San 
Marcos de Colon, 490m (D.HJanzen); 3.6mi W 
Choluteca, 200m (D.HJanzen); 7.4mi NE 
Choluteca, 150m (D.HJanzen); Colon: Trujillo, 
80m (Echternacht); Comayagua: 11.7mi S San 
Antonio, 830m (D.HJanzen); 4mi N Comayagua, 
500m (D.HJanzen); Cortes: 24.6mi SW San Pedro 
Sula, 240m (D.HJanzen); Francisco Morazdn: 
24.3mi S Camayagiiela (Tegucigalpa), 1000m 
(D.HJanzen); 30.4mi S Camayagiiela 
(D.HJanzen); 30.5mi S Camayagiiela, 930m 

(D.HJanzen); Ocotepeque: 2.3mi E [Nueva] 
Ocotepeque, 1090m (D.HJanzen); Nueva 
Ocotepeque, 910m (D.HJanzen); Santa Barbara: 
13.7mi SW Quimistan, 320m (D.HJanzen); Valle: 
18.5mi W Jicaro Galan (D.HJanzen); 4.6mi E 
Jicaro Galan, 190m (D.HJanzen). 

MEXICO Camp.: O.lmi S Tenabo, rd. to Becal 
(D.HJanzen); 0.8mi E Campeche (D.HJanzen); 
29mi E & 12mi S Campeche (Ruinas Edzna) 
(D.HJanzen); 29mi E Campeche (D.HJanzen); 
48mi NE Puerto Real (Isla Aguada), Hwy.l 80 
(D.HJanzen); 5mi S Tenabo (Campeche-Becal Rd.) 
(D.HJanzen); Campeche (N.L.H.Krauss); Chis.: 
2.4mi E Chiapa de Corzo, Hwy.190, 580m 
(D.HJanzen); 2kmN Yxhuatan [Ixhuatan], "2miN 
Tapilula" (D.HJanzen); 32mi W [San] Cristobal 
de las Casas, Hwy.190 (D.HJanzen); 3km ENE 
Chiapa de Corzo, 500m (P.S.Ward); 3mi N Soyalo 
[on Hwy.195] (D.HJanzen); 42.5mi S Comitan, 
Hwy.190, 680m(D.HJanzen); 5.4mi E Chiapa de 
Corzo, Hwy.190, 770m (D.HJanzen); 56.9mi NE 
[NW?] Tapachula [on Hwy.200?] (D.HJanzen); 
7.0mi NE [NW?] Tapachula [on Hwy. 200?] 
(D.HJanzen); 7.5mi NW Cd. Cuauhtemoc, 
Hwy.190 (D.HJanzen); 8.5mi S La Trinitaria, 
Hwy. 190 (D.HJanzen); FincaEsmeralda (R.Nettel 
F.); Puerto de San Benito [=Puerto Madero] 
(R.Nettel F.); Tonala, 40m (D.HJanzen); Yerba 
Santa (G.N.Collins); Hgo. : 2km W Orizatlan, 245m 
(W.MacKay); Oax.: 11.4-17.0mi W Tehuantepec 
(D.HJanzen); 19km N San Pedro Pochutla, 200m 
(W.MacKay); 3.9mi E Tehuantepec (D.HJanzen); 
5.7mi W "Tapanapec" [=Tapanatepec] 
(D.HJanzen); 6.0mi E Niltepec ,Hwy.l90, 100m 
(D.HJanzen); 8.1ml W Niltepec, Hwy.190, 60m 
(D.HJanzen); Temascal (D.HJanzen); Temascal, 
25m (D.HJanzen); Q.Roo: 12.2mi S Peto, Q.Roo- 
Yucatan border (D.HJanzen); 26.6mi S Felipe 
Carillo Puerto (D.HJanzen); 5.4mi E Polyuc 
(D.HJanzen); Cancun (A.Dejean); Cenote de Las 
Ruinas, 8km NW Polyuc (J.Red et al.); Chetumal 
(J.C. & D.Pallister); San Miguel, Cozumel I. 
(N.L.H.Krauss); Sian Ka' an (A.Dejean); Sian Ka' an 
Reserve, nr. Felipe Carillo Puerto (A.Dejean); 
S.L.P.: 2mi N Rio Amahac, Tamazunchale, 400ft. 
(W.S.Creighton); 6mi NW Tamazunchale, 
600ft.(Univ.Kansas Mex.Exped.); 8mi W San 
Joachin (W. J.Gertsch); El Bonito, 7mi S Cd. Valles, 

VOLUME 2, NUMBER 1, 1993 


300ft. (P.H. & M. Arnaud); El Salto (W.E.LaBerge); 
Tamazunchale (D.H.Janzen); Tamazunchale, 600ft. 
(W.S.Creighton); Ver.: 29.5mi NW Tuxpan, 
Hwy. 122 [actually Hwy. 127] (D.H.Janzen); Alazan 
(F.Parker & D.Miller); Cordoba (W.M.Mann); 
CotaxtlaExp. Sta.,Cotaxtla (D.H.Janzen); Mirador 
(E.Skwarra); Veracruz (E.Skwarra); Yuc.: 30mi S 
Merida (P.J.Spangler); 8mi E Merida (rd. to Pto. 
Juarez) (D.H.Janzen); Itzimna (J.C. & 
D.Pallister);Merida (D.H.Janzen; N.L.H.Krauss); 
Oxkutzcab (D.H.Janzen); Sta. Elena, S of Ticul, 
"Hwy.180" [prob.Hwy.261] (D.H.Janzen); state 
unknown: "Mex"("Norton"). 

NICARAGUA Estelt: Imi N Condega, 500m 
(D.H.Janzen); 2.5mi N Condega, 620m 
(D.H.Janzen); Leon: San Jacinto (J.M.Maes); 
Madriz: 3mi W Somoto, 650m [=2.5mi W Somoto] 
(D.H.Janzen); Nueva Segovia: 7. Imi W Amatillo 

Pseudomyrmex satanicus (Wheeler 1942) 
(Figs. 10, 20, 59, 68) 

Pseudomyrma satanica Wheeler 1 942: 1 74. Syntype 
workers, queen, male, Rio Agua Salud, Canal 
Zone, Panama (W. M. Wheeler) (AMNH, 
LACM, MCZC) [Examined]. One MCZC 
syntype worker here designated LECTOTYPE. 
Pseudomyrmex satanica [sic] (Wheeler); Janzen 


Pseudomyrmex satanicus (Wheeler); Kempf 

Worker measurements (n= 15). HL 1.16-1.36, 
HW 1.10-1.26, MFC 0.035-0.057, CI 0.90-0.97, 
REL 0.45-0.50, REL2 0.48-0.52, OOI 0.92-1.67, 
VI 0.69-0.78, FCI 0.030-0.049, SI 0.45-0.49, SI2 
0.88-1 .00, NI 0.63-0.68, PLI 0.47-0.54, PWI 0.46- 
0.63, PPWI 1.35-1.54. 

Worker diagnosis. Similar to P. spinicola (q.v.) 
except as follows. Larger (HW > 1 .09), head broader 
(CI > 0.88) (Fig. 34) with straight or slightly con- 
cave posterior margin and subangulate posterolat- 
eral corners (Fig. 10). (The posterior margin of the 
head approaches this condition in some P. spinicola 
workers but these have much smaller, more elon- 
gate heads, HW < 1 . 10, CI < 0.90.) Median clypeal 
lobe narrower (CLW/HW 0.20-0.22; see Fig. 33). 

Palp formula 4,3. Head with pronounced pit-like 
impression below the median ocellus (absent or 
poorly developed in P. spinicola). Metanotal groove 
better developed, longer. Petiole tending to be 
more slender, with less distinct posterolateral cor- 
ners (this characteristic seen in some workers of P. 
spinicola, especially individuals from Panama). 
Body pubescence averaging thicker than in P. 
spinicola. Dark brown in color, mandibles and 
appendages lighter. 

Comments. The foregoing diagnosis will al- 
low discrimination of P. satanicus workers from 
those of the closely related P. spinicola; queens can 
be recognized by size alone (HL > 1.65, HW > 
1.20). P. satanicus can be distinguished from the 
remaining members of the P.ferrugineus group by 
the emarginate, laterally angulate median clypeal 
lobe of the worker and the large size of the queen. 

Distribution and biology. P. satanicus is a 
forest species restricted to a few localities in central 
Panama where its host plant, Acacia melanoceras, 
grows (Fig. 68). Both the ant and plant are intoler- 
ant of forest clearance and are considered vulner- 
able to extinction (Janzen 1974). The ant is polygy- 
nous, with 5-20 or more queens per colony, and the 
workers are particularly aggressive, even for aca- 
cia-ants (Wheeler 1942; Janzen 1974). See Janzen 
(1974:43-53) for additional details on P. satanicus 
and its host plant. 

Material examined (AMNH, LACM, MCZC, 

PANAMA Canal Zone: "Canal Zone" 
(A.H.Jennings); 3miSWGatun Dam (D.H.Janzen); 
Barro Colorado Island (D.H.Janzen); France Field 
(G.C. Wheeler); Marajal [Majagual] nr. Colon 
(W.M. Wheeler); Red Tank (W.M.Wheeler); Rio 
Agua Salud (W.M.Wheeler); Zorra Island 
(D.H.Janzen); Panama: Rio Piedras (D.H.Janzen); 
prov. unknown: "Panama"(c.u.). 

Pseudomyrmex spinicola (Emery 1 890) 
(Figs. 11,21,60,68) 

Pseudomyrma spinicola Emery 1890:64. Lecto- 
type worker, Alajuela, Costa Rica (Alfaro) 
(MCSN) [Examined]. 

Pseudomyrma spinicola race atrox Forel 1912:24. 



Syntype workers, Panama (Christophersen) 
(MHNG, NHMB) [Examined]. Syn. nov. One 
syntype from MHNG here designated LECTO- 

Pseudomyrma spinicola race Gaigei Forel 
1914:615. Syntype workers, Columbien (Gaige) 
(MHNG), Fundacion, Colombia (F. M. Gaige) 
(LACM, MCZC) [Examined]. Syn. nov. 

Pseudomyrma spinicola subsp. infernalis Wheeler 
1942:180. Syntype workers, queens, males, 
Venado, Canal Zone, Panama (W. M. Wheeler), 
Red Tank, Canal Zone, Panama (W. M. Wheeler), 
and Las Sabanas, Panama (W. M. Wheeler) 
(AMNH, MCZC) [Examined]. One MCZC 
worker, from Red Tank, here designed LECTO- 
TYPE. Syn. nov. 

Pseudomyrma spinicola subsp. scelerosa Wheeler 
1942:181. Syntype workers, Granada, Nicara- 
gua (C. F. Baker) (AMNH, MCZC) [Exam- 
ined] . One MCZC worker here designated LEC- 
TOTYPE. Syn. nov. 

Pseudomyrma spinolae [sic] var. infernalis 
Enzmann 1945:91. Syntype workers, queens, 
Red Tank, Canal Zone, Panama (W. M. Wheeler) 
(MCZC) [Examined] [Objective synonym of P. 
spinicola subsp. infernalis Wheeler; Brown 

Pseudomyrma spinolae [sic] var. scelerosa 
Enzmann 1945:91. Syntype workers, Granada, 
Nicaragua (C. F. Baker) (MCZC) [Examined] 
[Objective synonym of P. spinicola subsp. 
scelerosa, Wheeler; Brown 1949:43]. 

Pseudomyrmex spinicola (Emery); Wheeler and 
Wheeler 1956:386. 

Worker measurements (n = 41). HLO.99-1.28, 
HW 0.94-1.15, MFC 0.032-0.067, CI 0.84-0.97, 
REL 0.42-0.47, REL2 0.45-0.54, OOI 1.22-2.77, 
VI 0.64-0.83, FCI 0.032-0.061, SI 0.45-0.50, SI2 
0.88-1.05, NI 0.61-0.69, PLI 0.47-0.64, PWI 0.49- 
0.71, PPWI 1.32-1.85. 

Worker diagnosis. Median clypeal lobe emar- 
ginate, laterally angulate (Fig. 11), relatively broad 
(CLW/HW 0.21-0.25). Palp formula 5,3 (rarely 
5p4,3). Frontal carinae relatively close, and me- 
dian lobes of antennal sclerites rather exposed 
(FCI2 0.24-0.42). Head longer than broad but 
variably so (see range of CI values). Posterior 

margin of head ranging from broadly convex (Fig. 
11) to straight or even weakly concave, usually 
rounding gently into the sides of head. Basal face 
of propodeum subequal to declivitous face, round- 
ing into latter; in dorsal view propodeal spiracles 
salient,protruding laterally. Petiole generally slen- 
der (PLI <0.65) with a well developed anterior 
peduncle; in dorsal view posterolateral angles typi- 
cally prominent. Head densely punctulate, sublucid, 
interspaces small (punctulae essentially contigu- 
ous on most of head) but shiny. Mesosoma finely 
punctulate dorsally becoming punctulate-coriarious 
laterally, sublucid; propodeum lacking overlying, 
coarser rugulo-punctate sculpture. Standing pilos- 
ity usually moderately common on body dorsum 
and including some hairs > 0.20 mm. Appressed 
pubescence common on most surfaces. Varying 
from light orange-brown to dark brown in color. 

Comments. The short, broad, emarginate and 
laterally angulate median clypeal lobe (Fig. 11) 
distinguishes the worker of this species. The 
sublucid integument, elongate petiole, prominent 
propodeal spiracles, and somewhat angulate poste- 
rolateral corners of the petiole are also characteris- 
tic. In addition, queens and workers of P. spinicola 
have more elongate scapes and legs than those of all 
other species except P. satanicus(Figs. 30,31). For 
differences between P. spinicola and the closely 
related P. satanicus see under the latter species. 

P. spinicola is a variable taxon and has received 
several infraspecific names, here considered junior 
synonyms. Southeastern populations (from the Rio 
Grande de Tarcoles in Costa Rica east through 
Panama to northern Colombia) are somewhat dif- 
ferentiated from the others, with the workers and 
queens tending to have more elongate heads, darker 
color, and more slender petioles with less pro- 
nounced posterolateral angles (see Figs. 34, 35). In 
Costa Rica the contrasts between the two sets of 
populations are rather striking, and are perhaps 
accentuated by habitat differences since some (but 
not all) the southeastern populations are associated 
with Acacia allenii growing in forested situations, 
while the northern populations are primarily from 
Acacia collinsii in open habitats. Samples from 
Panama (all associated with A. collinsii) are more 
variable and partly bridge the phenotypic gap. It is 
possible that more than one species is masquerad- 

VOLUME 2, NUMBER 1, 1993 


ing in this variation but the evidence remains am- 

Distribution and biology. P. spinicola is a 
monogynous species, distributed from Honduras to 
northern Colombia (Fig. 68), which is associated 
with Acacia collinsii and, less frequently, Acacia 
allenii and A. cornigera. Janzen (1983) provides a 
good summary of its biology in Costa Rica, under 
the name "P. ferruginea". Observations on "P. 
ferruginea" in Costa Rica, Nicaragua, Panama and 
Isla Providencia (Janzen 1969, 1974, 1975, 1983) 
refer to P. spinicola', true P. ferrugineus does not 
occur south of Honduras and El Salvador. 

Material examined (AMNH, ANSP, BMNH, 

COLOMBIA Atlantico: Cuatro Bocas, 200m 
(J. F.G.Clarke); Bolivar. Hda. Monterey, 50m 
(G.Fagua; F.Fernandez); Magdalena: Aracataca 
(P.J.Darlington); Fundacion (F.M.Gaige); 
Fundacion, Santa Marta Mts.,300ft. (F.M.Gaige); 
San Andres y Providencia: "Old Providence Isl." 
(D.Fairchild); Isla Providencia, 300ft.(D.H.Janzen); 
dept. unknown: "Columbien" (Gaige). 

COSTA RICA Alajuela: Alajuela (A.Alfaro); 
San Mateo (P.Biolley); Surubres, nr. San Mateo 
(P.Biolley); Turriicares (A.Alfaro); Cartago: 
Turrialba (c.u.); Guanacaste: 10.7mi NW Liberia 
(D.H. Janzen); 2mi S Canas (D.H. Janzen); 5km S 
Liberia (D.H.Janzen); 6mi W Liberia (D.H.Janzen); 
7km N Canas (D.H.Janzen); Canas, "La Pacifica" 
(R.L.Jeanne); Finca La Pacifica (D.W.Davidson); 
Garita (A.Alfaro) ; Hda. Comelco, 24km NW Canas 
(InterAm Hwy) (E.R.Heithaus); Hda. La Pacifica, 
nr. Canas, 50m (P.S.Ward); Palo Verde (D.E.Gill; 
E.Guerrant & P.Fiedler; H.A.Hespenheide; 
D.H. Janzen) ;Palo Verde, 50m (D.M.Olson); Palo 
Verde, < 1 00m (J.Longino) ; Rio Corobici, nr. Canas 
(R.M.Bohart); Santa Rosa Natl. Pk.(E.M.Barrows); 
Santa Rosa Natl. Pk., 5m (P.S.Ward); Santa Rosa 
Natl. Pk., <5m (P.S.Ward); Heredia: "15mi SE 
Pto.Viejo" [15km SW Pto.Viejo] (D.H.Janzen); 
Puntarenas: l-5mi NW Rincon (D.H.Janzen); 
14.1mi N Golfito (D.H.Janzen); 14km E Palmar 
Norte, 70m (P.S.Ward); 1km NE Tarcoles, 20m 
(P.S.Ward); 21.6 rd.mi NE Palmar Norte, 90m 

(D.H.Janzen); 3.4miSEGolfito, 30m (D.H.Janzen); 
4mi SW Rincon (D.H.Janzen); Corcovado Natl. 
Pk. (D.W.Davidson; J.T.Longino); Corcovado Natl. 
Pk., Llorona (J.T.Longino); Corcovado Natl. Pk., 
Sirena, 100m (P.S.Ward); Corcovado Natl. Pk., 
Sirena, 10m (P.S.Ward); Entrada Boruca, 20km 
NE Palmar Sur (D.H.Janzen) ; Osa Penin., nr. Rincon 
(D.H.Janzen); Reserva Biol. Carara, 30m 
(P.S.Ward);Rincon (D.H.Janzen); Rio Terraba, nr. 
Palmar Sur (D.H.Janzen); San Jose: 16.4mi SW 
Sanlsidro, 160m (D.H. Janzen); 3. 5km NE Santiago 
de Pur (D.H.Janzen); Santa Ana (D.H.Janzen); 
Tarrazu [Rio?] (A.Alfaro); Villa Colon (A.Alfaro; 
D.H.Janzen); Villa Colon, 880m (A.Alfaro). 

HONDURAS Choluteca: 1 1 . 1 mi NE Choluteca, 
450m (D.H.Janzen); 3.6mi W Choluteca, 200m 
(D.H.Janzen); Colon: El Canal, Puerto Castilla 
(W.M.Mann); Roetan Isl. [Isla de Roatan] 
(M.Bates); Trujillo, 80m (Echternacht). 

NICARAGUA Boaco: Empalme do Boaco 
[=ElEmpalme?] (Echternacht); Chontales: no spe- 
cific locality (Janson); Esteli: 7.5mi NW San Isidro, 
550m (D.H.Janzen); Granada: Granada 
(C.F.Baker); Leon: 19mi SE Leon [=3.5mi N 
Pto.Somoza (Sandino)] (D.H.Janzen); 28.1mi SE 
Leon (D.H.Janzen); Madriz: 13.9mi from Hondu- 
ras, on Nic.border, Hwy.l (D.H.Janzen); 2.5mi W 
Somoto (D.H.Janzen); Managua: 20mi N Tipitapa, 
90m [=19.4mi N Tipitapa] (D.H.Janzen); 8.1mi E 
San Benito (D.H.Janzen); 9mi N Tipitapa, 50m 
[=8.8mi N Tipitapa] (D.H.Janzen); Matagalpa: 
15.8mi NW Sebaco (D.H.Janzen); 2.6mi N Dario 
(D.H.Janzen); 4.1mi S Matagalpa, 650m 
(D.H.Janzen); 4mi S Dario, 350m [=4.5mi SE Dario] 
(D.H.Janzen); 4mi S Dario, 350m (D.H.Janzen); 
Rivas: C.R. border, Imi N Penas Blancas, <5m 
[=lmi NW Penas Blancas] (D.H.Janzen); Isla 
Ometepe (F.Joyce); San Juan del Sur, 10m [=lmi N 
San Juan del Sur] (D.H.Janzen). 

PANAMA Canal Zone: 7.5mi NW Balboa 
(between Summit Gdn. &Paraiso) (D.H.Janzen); 
Ancon (S.F.Blake); Barro Colorado Island (We- 
ber); Cerro Galera (P.S.Ward); Chivachiva trail 
(W.M.Wheeler); Chivachiva trail, nr. Red Tank 
(W.M.Wheeler); Culebra [presumably CulebraCut] 
(D.D.Gaillard); E end of Madden Dam 
(D.H.Janzen); Gamboa (N.Banks); Howard AFB, 



W of Panama City, 50m (W.L.Brown et al.); Mad- 
den Dam (D.Quintero et al.); Paraiso (A.Busck); 
Red Tank (W.M. Wheeler); Ruta 1, 14kmWPanama 
City, 100m (W.L.Brown et al.); Venado 
(W.M. Wheeler); W end Madden Dam 
(D.HJanzen); Chiriqui: 10.7mi ESE Concepcion 
(D.H.Janzen); 12.9mi E Remedies (D.HJanzen); 
19.6mi E Sapotilla, 50m (D.HJanzen); 7.2mi W 
Remedies (D.HJanzen); 9.5mi S Boquete, 620m 
(D.HJanzen); Code: 0.3mi W Agua Dulce, 50m 
(D.H.Janzen); 10.4miNE SantaMaria, 60m [=1 .9mi 
W Agua Dulce, Hwy. 1] (D.HJanzen); 2.7mi SW 
Penonome (D.H.Janzen); Herrera: Cerro 
Guacamaya, Albina al N. de Monagrillo (D.Quintero 
et al.); Los Santos: 3.1mi N Pedasi (D.HJanzen); 
Azuero Penin., 5.4mi SE Los Santos, <5m 
(D.H.Janzen); Panama: 18.6mi SW Chepo 
(D.HJanzen); Bella Vista (N.Banks); Las Sabanas 
(G.C.Wheeler; W.M.Wheeler); Las Sabanas, 
Panama City (H.F.Dietz); Rio Corona, S of El 
Valle, 2000ft. (C.W.Rettenmeyer); Rio Tetita, San 
Carlos (F.D.Rattinibane); savannah nr. Juan Diaz 
(Weber); Veraguas(l): LasPalmas (c.u.); Veraguas: 
4km NW Santiago (D.Quintero); prov. unknown: 
"Panama" (Christophersen). 

Pseudomyrmex veneficus (Wheeler 1942) 
(Figs. 17, 28, 62, 69) 

Pseudomyrma belli subsp. venefica Wheeler 
1942:162. Syntype workers, males, queens, 
Escuinapa, Sinaloa, Mexico (J. H. Batty) 
(AMNH, MCZC) [Examined]. One MCZC 
syntype worker here designed LECTOTYPE. 

Pseudomyrma belli subsp. venifica Enzmann 
1945:81. Syntype workers, queens, Manzanillo, 
Colima, Mexico (C. H. T. Townsend) (MCZC) 
[Examined] [Synonymy by Brown 1949:42]. 

Pseudomyrmex venefica [sic] (Wheeler); Janzen 

Pseudomyrmex belli veneficus (Wheeler); Kempf 

Pseudomyrmex veneficus (Wheeler); Ward 

Worker measurements (n= 12). HLO.95-1.04, 
HW 0.85-0.95, MFC 0.045-0.073, CI 0.88-0.95, 
REL 0.44-0.47, REL2 0.47-0.52, OOI 1.26-2.30, 

VI 0.66-0.75, FCI 0.051-0.081, SI 0.43-0.46, SI2 
0.85-0.94, NI 0.58-0.65, PLI 0.60-0.67, PWI 0.58- 
0.67, PPWI 1.35-1.73. 

Worker diagnosis. Similar to P. ferrugineus 
(q.v.) except as follows. Smaller (LHT 0.69-0.80), 
with broad head (CI > 0.87); frontal carinae sepa- 
rated by basal scape width or less (FCI2 0.40-0.60); 
petiole short (PL 0.43-0.54) and relatively narrow 
(see PWI values) with somewhat rounded postero- 
lateral angles (Fig. 28). Head densely punctulate, 
subopaque to sublucid, with weak silvery reflec- 
tance. Overlying rugulo-punctate sculpture on 
propodeum weak and ill-defined. Standing pilosity 
variable in abundance, becoming rather short ( 
0.10 mm) and sparse in southern populations. Pu- 
bescence thick and conspicuous, suberect on some 
surfaces especially the propodeum and petiole; 
suberect pubescence on petiolar dorsum contrast- 
ing with the appressed pubescence on the postpetiole 
(Fig. 28). Very dark greyish-brown to black, parts 
of the mesosoma and petiole sometimes with lighter 
yellowish brown (more consistently so in the queen). 

Comments. The small size (worker HW < 0.96; 
queen HW 0.84-0.96, n=12), conspicuous suberect 
pubescence on the propodeum and petiole, and 
black coloration of the head and gaster distinguish 
workers and queens of P. veneficus. The related 
species, P. flavicornis, is larger (worker HW > 
0.98, queen HW 1.12-1.19) with a broader and 
more robust petiole (Figs. 25, 28). Workers and 
queens of P. flavicornis also lack the sublucid head 
and conspicuous suberect pubescence characteris- 
tic of P. veneficus. P. mixtecus is somewhat inter- 
mediate between these two - it has the head sculp- 
ture and pubescence typical of P. flavicornis but 
approaches P. veneficus in size (worker and queen 
head widths overlapping, although only slighter in 
the queens where HW 0.96-1.01 (n=8) in P. 
mixtecus) and petiolar dimensions (Figs. 44-47). 

Distribution and biology. P. veneficus has a 
limited distribution in western Mexico (Sinaloa to 
Michoacan) (Fig. 69) where colonies occupy Aca- 
cia hindsii and, at one locality, A. collinsii. Janzen 
(1973) gives a detailed description of the ecology 
and behavior of this highly polygynous, effectively 
unicolonial, species whose colonies are among the 
largest of all social insects (containing millions of 
workers and several hundred thousand queens). 

VOLUME 2, NUMBER 1, 1993 


Material examined (AMNH, CASC, EBCC, 

MEXICO Col: 9 Ami NW Manzanillo 
(D.H.Janzen); Manzanillo (C.H.T.Townsend; 
W.M.Wheeler); Paso del Rio, 200ft. (IJ.Cantrall); 
JaL: 2km E Chamela, 20m (P.S.Ward); 5km E 
Chamela, 50m (P.S.Ward); 6mi NE El Rincon, 
1600ft. (R.J.Hamton); Barra de Navidad 
(N.L.H.Krauss); Chamela (RJ.McGinley; 
J.F.Watkins);M/c/z.: 1.1 mi N Gabriel Zamora, 820m 
(D.H.Janzen); 1.5miNLaMira (D.H.Janzen); 15km 
WNW Playa Azul, 50m (P.S.Ward); Nay.: 12mi 

NE San Bias (W.J.Gertsch & W.Ivie); 16mi NW 
Tepic (W.E.LaBerge); 3 Imi N Tepic (D.H.Janzen); 
37mi N Tepic (D.H.Janzen); 4mi E San Bias 
(M.E.Irwin); Rio Palillo, 14mi E San Bias 
(D.H.Janzen); Sin.: 14.6mi S Mazatlan 
(D.H.Janzen); 20mi E Villa Union (E.I.Schlinger); 
20mi E Villa Union, 235m (M.E.Irwin; E.Schlinger 
et al.); 20mi S Villa Union (E.I.Schlinger); 5mi E 
Concordia (W.J.Gertsch & J.A.Woods); Escuinapa 
(J.H.Batty); Palmito ( Mauzo); Piedra Blanca 
(R.M.Bohart); state unknown: "Mexico"(c.u.). 


ferrugineus group 


V spinicola + satanicus 

Figs. 67- 72. Distributions of species in the Pseudomyrmex ferrugineus group. 





Three of the species discussed below 
(Pseudomyrmex nigropilosus, P. simulans and P. 
subtilissimus) are obligate inhabitants of Central 
American swollen-thorn acacias, although they are 
not closely related to the P. ferrugineus group 
(Ward 1991). A fourth species, P. reconditus, is 
known only from a single collection, made in 
association with Acacia collinsii. The remaining 
six species (P. boopis, P. gracilis, P. hesperius, P. 
ita, P. kuenckeli and P. opaciceps) are non-special- 
ist Pseudomyrmex which have been collected only 
occasionally from acacias. These taxa are included 
for completeness, and their presentation here ne- 
cessitates a certain amount of taxonomic house- 

One could expect additional generalist 
Pseudomyrmex to be found in living or dead acacia 
thorns. Menozzi (1927b) mentions collections by 
H. Schmidt of "Pseudomyrma flavidula" and "P. 
brunnea" from Acacia "spadicigera" (probably A. 
collinsii) near San Jose, Costa Rica. I have not 
examined the ant specimens in question but they 
probably belong to P. pallidus (F. Smith) and P. 
ejectus (F. Smith), respectively. Diagnoses of these 
species appear in Ward (1985). Finally, mention 
should be made of other Neotropical acacias which 
are apparently not myrmecophytes, but which may 
harbor opportunistic Pseudomyrmex species in their 
spines: Acacia daemon in Cuba with P. pazosi, P. 
simplex and P. cubaensis (Berazain & Rodriguez 
1983; Pseudomyrmex nomenclature follows Ward 
1989), and A. coven in Paraguay with P. gracilis 
(s.l.) and one or more species in the P. pallidus 
group (Wheeler 1942; Ward 1991). 

Synonymic list of species 

P. boopis (Roger 1863b) 

= P. modestus (F. Smith 1862) (preoccupied) 
= P. thoracicus (Norton 1868b) syn. nov. 
= P. excavatus (Mayr 1870) (Kempf 1967) 
= P.flaviventris (Emery 1896) (Kempf 1960) 
= P.fusciceps (Santschi 1931) (Kempf 1960) 

= P. guatemalensis (Enzmann 1945) (Kempf 

P. gracilis (Fabricius 1804) 

= P. bicolor (Guerin 1844) syn. nov. 

= P. sericatus (F. Smith 1855) syn. nov. 

= P. dimidiatus (Roger 1863a) syn. nov. 

= P. mexicanus (Roger 1863a) syn. nov. 

= P. variabilis (F. Smith 1877) (Ward 1989) 

= P. pilosulus (F. Smith 1877) syn. nov. 

= P. volatilis (F. Smith 1877) syn. nov. 

= P. canescens (F. Smith 1877) syn. nov. 

= P. guayaquilensis (Forel 1907) (unavailable 

= P. glabriventris (Santschi 1922) syn. nov. 

= P. veliferus (Stitz 1933) syn. nov. 

= P. longinodus (Enzmann 1945) (Brown 1949) 
P. hesperius, sp. nov. 
P. ita (Forel 1906) stat. nov. 

= P. acaciarum (Wheeler 1942) syn. nov. 

= P. acaciorum (Enzmann 1945) (Brown 1949) 
P. kuenckeli (Emery 1890) 

= P. dichrous (Forel 1904) (Kempf 1961) 

= P. bierigi (Santschi 1932) (Kempf 1961) 

= P. crenulatus (Enzmann 1945) (Kempf 1961) 
P. nigropilosus (Emery 1890) 
P. opaciceps, sp. nov. 
P. reconditus, sp. nov. 
P. simulans Kempf 1958 
P. subtilissimus (Emery 1890) 


Pseudomyrmex boopis (Roger 1863b) 
(Fig. 1) 

Pseudomyrma modesta F. Smith 1862:32. Holo- 
type (unique syntype) worker, Panama (Stretch) 
(BMNH) [Examined]. [Preoccupied by P. 
modesta F. Smith 1 860 = Tetraponera modesta 
(F. Smith).] 

Pseudomyrma boopis Roger 1863b:25. Replace- 
ment name for Pseudomyrma modesta. 

Pseudomyrma thoracica Norton 1868b:8. Syntype 
workers, Cordova, Mexico (Sumichrast) [Not 
examined; see comments below]. Syn. nov. 

Pseudomyrma excavata Mayr 1870:410. Syntype 
workers, "N. Granada" (BMNH, MHNG, 
NHMV) [Examined] [Synonymy by Kempf 

VOLUME 2, NUMBER 1, 1993 



Pseudomyrma excavata var. flaviventris Emery 
1896:2. Syntype workers, Darien, Panama 
(Festa) (MCSN, MHNG) [Examined] [Syn- 
onymy by Kempf 1960:22]. 

Pseudomyrma excavata var. fusciceps Santschi 
1931:271. Two syntype workers, France Field, 
Panama (A. Bierig) (NHMB) [Examined] [Syn- 
onymy by Kempf 1960:22]. 

Pseudomyrma spinicola subsp. modesta F. Smith; 
Wheeler 1942: 105. 

Pseudomyrma tenuis var. guatemalensis Enzmann 
1945:92. Holotype worker, Escuintla, Guate- 
mala [Not examined] [Synonymy by Kempf 

Pseudomyrmex boopis (Roger); Kempf 1967:2. 

Worker diagnosis. Medium-sized species (HW 
1 . 1 6- 1 .29) in the P. tenuis group, with a broad head 
(CI 0.92-1.02), tectiform and laterally rounded 
median clypeal lobe, large eyes (REL 0.66), and 
laterally marginate pronotum. Mesosoma arched 
and angular in profile; petiole short, high and thin, 
laterally marginate, with a gently ascending 
anterodorsal face which rounds into a much steeper 
(almost vertical) posterior face (Fig. 1). Standing 
pilosity sparse, lacking on the mesonotum, 
propodeum, and petiole. Color highly variable, 
ranging from light testaceous brown to bicolored 
orange and black (usually with the gaster and 
pronotum lightest in color) to dark brown. 

Taxonomic comments. For a more detailed 
description of this species see Kempf (1960:23). I 
have synonymized P. thoracicus (Norton) under P. 
boopis on the basis of Norton's (1868b) original 
description and the biological notes of Sumichrast 
in Norton (1868a). In combination these clearly 
suggest P. boopis rather than any other 
Pseudomyrmex known to occur in southern Mexico. 
Although the type material of P. thoracicus is 
presumably lost, additional indirect evidence of its 
identity can be found in Gustav Mayr's collection 
in Vienna (NHMV) where there is a P. boopis 
worker from Colombia ("Neugranada") identified 
by Mayr as "P. thoracica Norton". This take son 
added significance when it is realized that Mayr 
was apparently the recipient of some of Norton's 
material. During a brief visit to NHMV I noted 

specimens of several species, including P. 
ferrugineus, P. peperi, P. elongatulus (Dalla Torre) 
and P. brunneus (F. Smith) (although unfortunately 
not P. boopis), labelled "Mex. Norton" or "N. Am./ 

Distribution and biology. P. boopis occurs in 
rainforest and tropical moist forest from southern 
Mexico to Ecuador, Venezuela and northern Brazil. 
This species is less arboreal than most 
Pseudomyrmex, and nests typically in rotten wood 
on or near the ground. The type specimen of P. 
boopis came from a nest in a swollen-thorn acacia 
(Smith 1862:33), however, and Janzen found colo- 
nies in thorns of Acacia melanoceras seedlings in 

Pseudomyrmex gracilis (Fabricius 1 804) 
(Fig. 6) 

Formica gracilis Fabricius 1804:405. Lectotype 
worker, Essequibo, Guyana (ZMUC) [Exam- 

Pseudomyrma bicolor Guerin 1844:427. Syntype 
queen (unique?), Colombia (ZSMC) [Exam- 
ined] Syn. nov. 

Pseudomyrma sericata F. Smith 1855:159. Holo- 
type (unique syntype) worker, Brazil (BMNH) 
[Examined] Syn. nov. 

Pseudomyrma dimidiataRoger 1863a:177. Syntype 
workers, Colombia (not in MNHN or ZMHB) 
[Not examined] Syn. nov. 

Pseudomyrma mexicana Roger 1863a: 178. Syntype 
workers, Mexico (not in MNHN or ZMHB) 
[Not examined] Syn. nov. 

Pseudomyrma variabilis F. Smith 1877:62. Lecto- 
type worker, Barbadoes (BMNH) [Examined] 
[Synonymy by Ward 1989:439]. 

Pseudomyrma pilosula F. Smith 1877:62. Two 
syntype workers, Barbadoes (BMNH) [Exam- 
ined]. One syntype here designated LECTO- 
TYPE. Syn. nov. 

Pseudomyrma volatilis F. Smith 1877:65. Holo- 
type (unique syntype) male, Mexico (BMNH) 
[Examined] Syn. nov. 

Pseudomyrma canescens F. Smith 1877:66. Holo- 
type (unique syntype) queen, Abydos, Brazil 
(BMNH) [Examined] Syn. nov. 



Pseudomyrma gracilis var. glabriventris Santschi 
1922:345. Syntype workers, Izozo, Bolivia (Lizer 
& Deletang) (NHMB) [Examined] Syn. nov. 

Pseudomyrma gracilis mexicana var. 
guayaquilensis Forel 1907:7. Worker, 
Guayaquil, Ecuador (Buchwald) (MHNG) [Ex- 
amined] Unavailable infrasubspecific name. 

Pseudomyrma gracilis var. velifera Stitz 1933:68. 
Holotype queen, Champerico, Guatemala 
(Paessler) (not in ZMUH; Weidner 1972) [Not 
examined] Syn. nov. 

Pseudomyrma gracilis var. longinoda Enzmann 
1945:87. Syntype worker, Peru (MCZC) [Ex- 
amined] [Synonymy by Brown 1949:43]. 

Pseudomyrmex gracilis (Fabricius); Kusnezov 

Worker diagnosis. With the traits of the gracilis 
group (see couplet 6 of the key; p. 130) and the 
following more specific features. Head broad, about 
as wide as long (CI 0.95-1.08); anterior margin of 
median clypeal lobe straight to broadly convex, 
rounded laterally; pronotum dorsolaterally margin- 
ate but not sharply so; in lateral view mesonotum 
more steeply inclined than basal face of propodeum; 
petiole long and slender (PLI 0.46-0.57) with a 
distinct anterior peduncle (Figs. 6, 53); head densely 
punctulate with a subopaque to sublucid (not matte) 
appearance; standing pilosity abundant, fine, pre- 
dominantly pale silvery- white (not black). 

Size and color extremely variable (HW 1.39- 
2.07), varying from unicolorous black (appendages 
lighter) to unicolorous orange-brown, with many 
intermediate and bicolored combinations. In popu- 
lations from Mesoamerica the gaster is typically 
black, or if paler (orange-brown) then it is usually 
accompanied by a similar light coloration of the 
mesosoma (and sometimes also the head). 

Taxonomic comments. The P. gracilis com- 
plex presents one of the more taxonomically chal- 
lenging problems in the genus Pseudomyrmex and 
the above treatment is by no means a final solution. 
The worker- and queen-based forms, newly syn- 
onymized under P. gracilis, fall within the bounds 
of the preceding diagnosis, but it is quite possible 
that my concept of this species will prove to be too 
broad. The types of P. dimidiatus, P. mexicanus and 
P. veliferus could not be located. They are judged to 

be junior synonyms on the basis of the original 
descriptions. The unique male holotype of P. 
volatilis is clearly a member of the P. gracilis group 
based on size (HW 1.48), mandibular dentition, 
pilosity, petiole shape, and shape of the parameres. 
In comparison with males of gracilis group species 
known to occur in Mexico, namely P. gracilis, P. 
major (see below), P. nigropilosusandP. opaciceps, 
the type specimen agrees best with P. gracilis. 

The concept of P. gracilis adopted above en- 
compasses an impressive amount of phenotypic 
variability. Collections from single regions often 
give the impression that this variation is distributed 
bimodally or multimodally , as more or less discrete 
morphs. For example, nest samples from Costa 
Rica can be segregated on the basis of worker 
morphology into (i) a large (HW > 1.80), usually 
lighter-colored form (with orange mesosoma, peti- 
ole, and postpetiole, and black head and gaster), (ii) 
a smaller, bicolored, usually more heavily infuscated 
form, and (iii) an all-black form of variable size. 
The first two are typically found in open or xeric 
habitats while the third is more common in closed 
forest, suggesting some ecotypic differentiation. 
Yet when large enough sample sizes are obtained 
all degrees of intermediacy in size and color are 
encountered, and the variation in color (less so size) 
can be seen among individuals (workers and alate 
queens) from the same nest. Thus, if there are 
ecotypes they do not appear to be reproductively 

Left unresolved after the establishment of the 
above synonymy is the relationship of P. gracilis to 
the following nominal taxa: P. alternans (Santschi), 
P. gracilis atrinodus (Santschi), P. gracilis 
argentinus (Santschi) and P. santschii (Enzmann). 
But the following deserves recognition as a distinct 
species: Pseudomyrmex major (Forel 1899:91), 
stat. nov. (syntype worker, Pinos Altos, Chihua- 
hua, Mexico (Buchan-Hepburn) (BMNH) (exam- 
ined); original combination: Pseudomyrma gracilis 
var. major). Workers of P. major can be distin- 
guished from those of P. gracilis by their emargin- 
ate median clypeal lobe, less distinct anterior pe- 
duncle of the petiole, and larger average size. Males 
of P. major have broadened fore-tarsal segments. 
P. major is confined to western Mexico, where it 
occurs sympatrically with P. gracilis without show- 

VOLUME 2, NUMBER 1 , 1993 


ing signs of intergradation. 

Distribution and biology. Befitting its wide 
distribution (southern United States to Argentina 
and Brazil) and variable phenotype, P. gracilis can 
be found in a variety of habitats from mangroves 
and thorn scrub to rainforest. It is often particularly 
common in disturbed situations such as old fields, 
roadsides, and secondary forest. Nests are usually 
located in dead twigs or small branches, but there 
are a substantial number of records of colonies 
occupying swollen-thorn acacias in Central America 
(Mexico to Panama). In a few localities P. gracilis 
is a common acacia inhabitant and under these 
circumstances it may exhibit local adaptation and 
phenotypic differentiation (see also Wheeler 
1942:107). For example, Janzen collected a series 
of specimens from Acacia gentlei in Belize (15 mi. 
S Santa Elena) which have somewhat distinctive 
morphology: the workers are large, dark, abun- 
dantly hairy, and possess rather short petioles (PLI 
0.55), although none of these features is outside 
the total range of variation for the species. Janzen 
(1974:98) notes that the workers of this large black 
morph have atypically aggressive behavior. Given 
the kind of ecotypic variation to which P. gracilis is 
prone, it is not surprising to find a tendency of some 
populations to specialize on acacias. The ecology 
of this species is reminiscent of other animal spe- 
cies which show broad ecophenotypic variation, 
e.g. fish with trophic polymorphisms (Kornfield et 
al. 1982; Grudzien and Turner 1984; Sandlund et al. 

Pseudomyrmex hesperius Ward, sp. nov. 
(Fig. 4) 

Holotype worker. MEXICO Sinaloa: 15.9 mi. 
NE Concordia, Hwy. 40, 600m,, D. H. 
Janzen XVIII, ex Acacia hindsii (LACM). HW 
0.66, HL 0.83, EL 0.36, PL 0.34, PH 0.26. 

Paratypes. Same data as holotype: series of 1 1 

Additional non-type material. MEXICO 
Sinaloa: 14 km. S Mazatlan, 18.vii.1965, R. R. 
Snelling, 15 workers (LACM, MCZC, PSWC). 

Worker measurements (n=6). HL 0.78-0.85, 
HW 0.65-0.69, MFC 0.028-0.043, CI 0.79-0.83, 

REL 0.43-0.46, REL2 0.54-0.57, OOI 0.86-1.15, 
VI 0.75-0.82, FCI 0.043-0.062, SI 0.48-0.51, SI2 
0.87-0.93, FI0.41-0.45,PDI 0.84-0.95, MPI 0.053- 
PPWI 1.41-1.56. 

Worker diagnosis. Small species (see above 
measurements) with elongate, subrectangular head 
and short eyes (REL 0.43-0.46, OI 0.61-0.65). 
Masticatory margin of mandible with five teeth, the 
fourth tooth (counting from the apex) separated by 
a gap of ca. 0.05 mm from the apicobasal tooth; 
MD8/MD9 0.70; third and fourth teeth small, 
contrasting with the large subapical and apical teeth 
(the latter ca. 0.032 and 0.055 mm in length, respec- 
tively) ; mesial tooth on basal margin situated slightly 
closer to apicobasal tooth than to proximal tooth 
(MD4/MD5 0.65); palp formula 5,3; median 
clypeal lobe short, its anterior margin straight to 
weakly convex, sharply rounded laterally; mini- 
mum distance between frontal carinae subequal to 
or less than basal scape width; frontal carinae 
diverging anteriorly and fusing with the antennal 
sclerites; pronotum laterally rounded, without hu- 
meral angles; in lateral profile the mesonotum and 
basal face of propodeum slightly inclined anteri- 
orly, separated by a well developed metanotal groove 
(Fig. 4); basal face of propodeum rounding into the 
longer declivitous face, the latter somewhat con- 
cave in profile; petiole short, apedunculate, shaped 
as in Fig. 4, with a prominent triangular antero ventral 
tooth; in dorsal view petiole very broad anteriorly 
(PWI3 0.59-0.62); postpetiole broader than long, 
its anteroventral process small and inconspicuous. 
Mandibles finely striate; head punctulate on a 
smooth shining background, punctulae separated 
by one to several diameters on upper half of head, 
becoming denser towards the clypeus; mesosoma 
sublucid, with weak punctulate-coriarious sculp- 
ture; petiole, postpetiole and gaster shining, with 
very fine piligerous punctures. Standing pilosity 
common but short (< 0.10 mm) on most parts of 
body, lacking on outer faces of tibiae. Appressed 
pubescence widely distributed, moderately dense 
on abdominal tergite IV. Dark brown; mandibles, 
appendages and fronto-clypeal complex tending 
towards a lighter brown. 

Taxonomic comments. This is a taxonomi- 
cally isolated species, not belonging to any of the 



nine major species groups of Pseudomyrmex (see 
Ward 1989).ThesalientfeaturesofP. hesperius are 
small size (HW < 0.72), reduced mandibular denti- 
tion and palp formula, short truncate median clypeal 
lobe, short eyes (especially obvious in lateral view, 
such that OI > 0.60), short apedunculate petiole 
with a broad attachment to the propodeum (PWI3 
0.60), punctulate head sculpture, sublucid integu- 
ment, and short standing pilosity. Some of these 
traits are shared with two other Mesoamerican 
Pseudomyrmex, P. fervidus (F. Smith) and a re- 
lated undescribed species, but both of these are 
larger (HW > 0.70), with standing pilosity which is 
longer and more extensive (present on the outer 
faces of the tibiae). 

Biology. Although the type specimens of P. 
hesperius were collected from Acacia hindsii this 
species is not an obligate acacia inhabitant. The 
series from 14 km. south of Mazatlan was collected 
from dead branches of a woody plant, not Acacia 
(R. R. Snelling, pers. comm.). 

Pseudomyrmex ita (Forel 1906) stat. nov. 

(Fig. 2) 

Pseudomyrma sericea var. ita Forel 1906:230. 
Syntype workers, San Mateo, Costa Rica (P. 
Biolley) (MHNG) [Examined]. One syntype 
here designated LECTOTYPE. 

Pseudomyrma sericea var. acaciarum Wheeler 
1942:176. Syntype workers, Tumba Muerta 
Road, Panama (W. M. Wheeler) (LACM, 
MCZC) [Examined] Syn. nov. 

Pseudomyrma sericea var. acaciorum Enzmann 
1945:90. Syntype workers, Tumba Muerta Road, 
Panama (W. M. Wheeler) (MCZC) [Examined] 
[Objective synonym of Pseudomyrma sericea 
var. acaciarum Wheeler; Brown 1949:43]. 

Pseudomyrmex sericeus ita (Forel); Kempf 

Worker diagnosis. A medium-sized member 
(HW ca. 0.75-0.98) of the P. sericeus group, with 
large elongate eyes (REL 0.65), convex median 
clypeal lobe, subcontiguous frontal carinae (MFC 
0.02), and palp formula of 6,4. Head longer than 
broad (CI 0.85). Basal face of propodeum shorter 
than declivitous face and meeting the latter at an 

angle. Petiole short, high (PLI > 1.00), with sharp 
dorsolateral margins; in profile anterior and dorsal 
faces of petiole weakly differentiated, rounding 
sharply into the vertical posterior face (Fig. 2). 
Body with fine punctulate-coriarious sculpture, 
opaque. Standing pilosity very sparse; a pair of 
stout setae present on the pronotal humeri, petiole, 
and postpetiole. Dark brown-black, with lighter 
brown maculation variably present on the pronotum, 
petiole, postpetiole, fronto-clypeal complex, and 

Taxonomic comments. This is one of several 
species originally described as "varieties" of P. 
sericeus (Mayr). Workers of P. ita can be distin- 
guished from those of P. sericeus by the angulate 
shape of their petiole, especially in lateral view 
(Fig. 2); the petiole of P. sericeus is subtriangular in 
profile, with more gently rounded edges. 

Distribution and biology. P. ita occurs from 
Mexico to Colombia, and typically inhabits dead 
twigs or branches of various woody plants. It has 
been collected from thorns of Acacia cornigera in 
Mexico and A. collinsii in Costa Rica and Panama. 

Pseudomyrmex kuenckeli (Emery 1890) 
(Fig. 3) 

Pseudomyrma kuenckeli Emery 1890:62. Syntype 
workers, queens, Alajuela, Costa Rica (A. Alfaro) 
(MCSN) [Examined]. 

Pseudomyrmakuenckelivar. dichroaForel 1904:41. 
Syntype workers, Dibulla, Colombia (A. Forel) 
USNM) [Examined] [Synonymy by Kempf 

Pseudomyrma kuenckeli var. bierigi Santschi 
1932:412. Holotype worker, Juan Diaz, Panama 
(A. Bierig) (NHMB) [Examined] [Synonymy 
by Kempf 1961:402]. 

Pseudomyrma crenulata Enzmann 1945:84. Holo- 
type worker, "Guernavaca", Mexico (not in 
MCZC) [Not examined; but other P. kuenckeli 
workers in the MCZC from Cuernavaca, Mexico 
(Wheeler) evidently represent the source series] 
[Synonymy by Kempf 1961:402]. 

Pseudomyrmex kuenckeli (Emery); Kusnezov 

VOLUME 2, NUMBER 1 , 1 993 


Worker diagnosis. A member of the P. viduus 
group, easily recognized by the shiny broad head 
(CI 1.12), short eyes (REL 0.46), flattened 
mesosoma, blocky petiole, and abundant pilosity 
(Fig. 3). For further description see Kempf 

Distribution and biology. This is a widely 
distributed but generally uncommon species, found 
from Mexico to Argentina and Brazil. P. kuenckeli 
appears to have a preference for nesting in large 
dead branches, in somewhat open or seasonally dry 
forest. Its association with ant acacias is sporadic at 
best and based upon two records from Costa Rica: 
Emery (1891 : 168) reported a single specimen col- 
lected by Alfaro from a swollen-thorn acacia, and 
Menozzi (1927b) recorded a collection by H. 
Schmidt from Acacia "spadicigera" (probably a 
misidentification of A. collinsii) near San Jose. 

Pseudomyrmex nigropilosus (Emery 1 890) 
(Fig. 7) 

PseudomyrmanigropilosaEmery 1890:62. Syntype 
workers, Liberia, Costa Rica (A. Alfaro) (MCSN, 
MHNG) [Examined]. 

Pseudomyrmex nigropilosus (Emery); Kempf 

Worker diagnosis. With the traits of the P. 
gracilis group (see couplet 6 of key) and the follow- 
ing more specific features. Head longer than broad 
(CI 0.84-0.90); anterior margin of median clypeal 
lobe convex, conspicuously protruding; dorsolat- 
eral margination of pronotum usually blunt; 
mesonotum more steeply inclined than basal face 
of propodeum; petiole relatively robust (PLI 0.69- 
0.77) with a short anterior peduncle (Fig. 7, 53); 
head and mesosoma densely punctulate to 
coriarious-imbricate, and subopaque; standing pi- 
losity conspicuous on most of the body including 
the outer faces of the tibiae, consisting largely of 
black hairs, those on the petiole and propodeum 
long (> 0.20 mm) and curved. Color varying from 
concolorous orange-brown to bicolored orange and 
black to (western Mexico) predominantly black 
with orange mottling on the head, mesosoma, and 

Taxonomic comments. Among the 
Pseudomyrmex species recorded from swollen-thorn 
acacias, P. nigropilosus is easily identified by its 
elongate eyes and head (REL 0.55-0.59, CI 0.84- 
0.90), short petiole (PLI 0.69-0.77), and conspicu- 
ous black pilosity (Fig. 7). Kempf (1958) provides 
further descriptive details. 

Distribution and biology. P. nigropilosus is 
found from Nayarit, western Mexico to Guanacaste 
Province, Costa Rica, and is restricted to nesting in 
swollen-thorn acacias (including Acacia collinsii, 
A. cornigera and A. hindsii). It is a member of the 
P. gracilis group and therefore not closely related 
to the principal group of acacia-ants (P.ferrugineus 
group) . Janzen ( 1 975) points out that P. nigropilosus 
is essentially a parasite of the Pseudomyrmexl Aca- 
cia mutualism. It occupies abandoned or otherwise 
uninhabited plants and reaps the benefits of this 
association without protecting the acacia from her- 
bivores or competing plants. Additional informa- 
tion about the ecology of this species is given in 
Janzen (1975). 

Pseudomyrmex opaciceps Ward, sp. nov. 
(Fig. 5) 

Holotype worker. GUATEMALA Retalhuleu: 
Puente Samala, 3.8 mi. NE San Felipe, 24.vii. 1966, 
D. H. Janzen W006724966 (LACM). HW 1.43, HL 
1.42, EL 0.85, PL 0.89, PH 0.39. 

Paratypes, Series of 11 workers with same 
data as holotype; large series of ca. 60 workers and 
10 males with the same locality and collector as 
holotype but the following dates and collection 
numbers: 18.vii.1966 M002718966 (possibly mis- 
labelled - see below), 18.vii.1966 W002718966, 
18.vii.1966 W004718966, 18.vii.1966 
W0057 18966 (possibly mis-labelled - see below), 
23.vii.1966 W002723966, 24.vii.1966 
W001724966, 24.vii.1966 W003724966 (BMNH, 

Additional non-type material. Series of work- 
ers, queens, and males from six additional locali- 
ties. MEXICO Chiapas: 94.5 mi. SE Tonola (D. H. 
Janzen). GUATEMALA Retalhuleu: 2 mi.N Puente 
Samala, 3.8 mi. NE San Felipe (D. H. Janzen); 3 mi. 
N Puente Samala, 3.8 mi. NE San Felipe (D. H. 
Janzen); 5 mi. W Retalhuleu, Hwy. CA-2 at Rio Nil 



(D. H. Janzen); Guatemala: Ciudad de Guatemala 
(D. H. Janzen). EL SALVADOR La Libertad: 
Quezaltepeque (M. Irwin & D. Cavagnaro) (LACM, 

Worker measurements (n=14). HL 1.30-1.42, 
HW 1.33-1.43, MFC 0.040-0.058, CI 0.99-1.04, 
REL 0.57-0.61, REL2 0.56-0.61, OOI 0.14-0.68, 
VI 0.65-0.71, FCI 0.029-0.042, SI 0.46-0.50, SI2 
0.77-0.88,FI0.36-0.39,PDIL12-1.37,MPI 0.059- 
0.076, NI 0.65-0.70, PLI 0.42-0.47, PWI 0.38-0.43, 
PPWI 0.92-1. 16. 

Worker diagnosis. With the traits of the P. 
gracilis group (see couplet 6 of key) and the follow- 
ing more specific features. Head about as broad as 
long; anterior margin of median clypeallobe straight 
to weakly convex; pronotum with blunt dorsolat- 
eral margination ; mesonotum more steeply inclined 
than basal face of propodeum; petiole long and 
slender (see PLI and PWI values) with a distinct 
anterior peduncle (Fig. 6); head densely punctulate- 
coriarious and matte; standing pilosity abundant, 
pale silvery-white, not black. Color: head and 
mesosoma dark brown to black, mandibles and 
appendages lighter brown; petiole, postpetiole and 
gaster a contrasting pale luteous brown or orange- 
brown. Portions of the fronto-clypeal complex, 
malar area, and mandibles may also be luteous 

Taxonomic comments. This species is distin- 
guished from the closely related and sympatric P. 
gracilis by a modest but consistent difference in 
head sculpture. In workers and queens of P. 
opaciceps the punctulate-coriarious sculpture and 
associated dense pubescence obscure the sheen of 
the head, producing a matte appearance under soft 
light, while in P. gracilis the head remains at least 
weakly shining. In addition the workers and queens 
of P. opaciceps average smaller in size than those 
of P. gracilis and they have a more slender petiole 
(PLI < 0.48; see Figs. 5, 6, 53). Finally, P. opaciceps 
has a distinctive and largely invariant color pattern: 
the pale yellow or orange-brown petiole, postpetiole 
and gaster contrast with the much darker head and 
mesosoma. This is not observed in Central Ameri- 
can P. gracilis, although a similar color pattern 
occurs in some Colombian populations of P. gracilis, 
and it also seen in some individuals of the more 
distantly related South American species P. venustus 

(F. Smith). 

Among the P. opaciceps paratypes in LACM, 
the pinned specimens with Janzen collection num- 
bers M0027 1 8966 and W0057 1 8966 appear to have 
been mis-labelled. In the Janzen alcohol collection 
samples M0027 18966 and W0057 18966 contain 
colony series of two quite different species (in the 
P.ferrugineus andP. pallidus groups, respectively); 
but there are two other alcohol samples from the 
same date and locality (W0027 18966 and 
W0047 18966) which are of P. opaciceps. I con- 
clude that a frame-shift occurred in the process of 
labelling the pinned series of specimens, producing 
the labelling error (this has happened to a substan- 
tial number of P. ferrugineus group collections - 
see "Materials and Methods" section). The remain- 
ing paratype (and non-type) material of P. opaciceps 
appears to be correctly labelled. 

Biology. P. opaciceps is evidently a generalist 
twig-nesting Pseudomyrmex, but Janzen also col- 
lected it from an Acacia cornigera tree overgrown 
by vines and unoccupied by the P. ferrugineus 
group (5 mi. W Retalhuleu, Guatemala, collection 
numbers M010714966-A and M010716966-D). 

Pseudomyrmex reconditus Ward, sp. nov. 
(Fig. 8) 

Holotype worfcer NICARAGUA, Madriz: 2.0 
mi. S Honduran border,Hwy 1, 840m, 29.vii.1967, 
mi. 8207.2, D. H. Janzen, ex Acacia collinsii 

Paratypes. One worker, one dealate queen, 
same data as holotype (LACM). 

Holotype andparatype worker measurements. 
HL 1.54, 1.44, HW 1.54, 1.47, MFC 0.071, 0.056, 
EL 0.93, 0.86, PL 0.88, 0.78, PH 0.57, 0.47, CI 
1.00, 1.02, OI 0.52, 0.52, REL 0.61, 0.59, REL2 
0.61, 0.58, OOI -0.01, -0.01, VI 0.73, 0.71, FCI 
0.046, 0.038, SI 0.47, 0.47, FI 0.44, 0.39, PDI 1.21, 
1.12, MPI 0.067, 0.061, NI 0.62, 0.64, PLI 0.64, 
0.60, PWI 0.57, 0.53, PPWI 1.40, 1.25. 

Paratype queen measurements. HL 1 .79, HW 
1.66, MFC 0.065, EL 1.02, PL 1.21, PH 0.75, CI 
0.92, OI 0.5 1, REL 0.57, REL2 0.62, OOI 0.22, VI 
0.79,FCI 0.039, SI 0.45, FI 0.46, NI 0.61, PLI 0.62, 
PWI 0.61, PPWI 1.53. 

Worker diagnosis. With the traits of the P. 

VOLUME 2, NUMBER 1 , 1993 


gracilis group (see couplet 6 of key) and the follow- 
ing more specific features. Head as broad as long; 
anterior margin of median clypeal lobe slightly 
convex, rounded laterally; pronotum with blunt 
dorsolateral margination; mesonotum more steeply 
inclined than basal face of propodeum; petiole of 
moderate length, high (PLI 0.60-0.64), with a dis- 
tinct anterior peduncle but without a well devel- 
oped anteroventral tooth (Figs. 8, 53), and lacking 
sharp dorsolateral margination; postpetiole notably 
broader than long. Mandibles weakly striolate, 
sublucid, becoming shagreened basally; head and 
mesosoma densely but finely punctulate-coriarious 
to coriarious-imbricate, subopaque; petiole, 
postpetiole, and gaster with fine piligerous punc- 
tures, obscured from view by the associated pubes- 
cence. Standing pilosity only moderately dense but 
with some apparent loss due to abrasion of the type 
specimens; hairs mostly black, not silvery-white, 
present on the head, mesosoma dorsum, petiole, 
and postpetiole; at least some moderately long 
(0.23-0.27 mm) hairs on the propodeum and peti- 
ole; one or two short hairs present on the outer faces 
of the meso- and meta-tibiae, the others possibly 
worn off; fine appressed golden pubescence present 
on most of the body. Head and mesosoma black, 
gaster dark brown, petiole and postpetiole orange; 
appendages brown, with orange flecking on the 

Taxonomic comments. This species is known 
only from the types. It is readily distinguished from 
all other acacia-associated species in the P. gracilis 
group by the combination of broad head (see CI 
values), robust petiole (PLI 0.60-0.64), and black 
pilosity. P. reconditus is similar to an undescribed 
Pseudomyrmex species collected from Tachigali in 
northern Peru (P. sp. PSW-35) but the latter has a 
shorter petiole, more extensive silvery-white pilos- 
ity and pubescence, and is all black in color. 

Biology. The type collection from Acacia 
collinsii is the only record. A single worker of P. 
nigropilosus occurred in the same alcohol vial as 
the workers and queen of P. reconditus. It remains 
to be confirmed that P. reconditus is confined to 
nesting in swollen-thorn acacias. 

Pseudomyrmex simulans Kempf 1958:459. Holo- 
type worker, Tumba Muerta Road, Panama (W. 
M. Wheeler) (MCZC) [Examined]. 

Worker diagnosis. With the traits of the P. 
gracilis group (see couplet 6 of key) and the follow- 
ing more specific features. Head longer than broad 
(CI 0.86-0.90); anterior margin of median clypeal 
lobe straight to broadly convex, rounded laterally; 
pronotum with sharp dorsolateral margination; 
mesonotum more steeply inclined than basal face 
of propodeum; petiole relatively short and high 
(PLI 0.61-0.66), with a distinct anterior peduncle 
(Figs. 9, 53), and with moderate dorsolateral mar- 
gination; head and mesosoma finely punctulate- 
coriarious to coriarious-imbricate, subopaque; 
standing pilosity rather short, pale and inconspicu- 
ous, present on the mesosoma dorsum and (usually) 
outer surfaces of the tibiae, but sometimes lacking 
or worn off on the latter; fine appressed pubescence 
on most of body; dark brown-black in color, distal 
portions of appendages lighter; mandibles luteous. 

Taxonomic comments. This curious species 
bears a superficial resemblance to the obligate 
acacia-ants (P. ferrugineus group), although its 
affinities to other/ 3 , gracilis group species are clear 
from eye size, pilosity, palp formula, mesosomal 
structure, and male genitalia. P. simulans can be 
recognized by the combination of elongate eyes 
(REL 0.52-0.55), short petiole (PLI 0.61-0.66), 
short inconspicuous pilosity, and black color. 

Distribution and biology. P. simulans is known 
only from a few collections, all from swollen-thorn 
acacias (A. collinsii), in Panama (Canal Zone and 
the provinces of Veraguas, Los Santos and Panama). 
Nothing has been published about its nesting biol- 
ogy or behavior, but Janzen's field notes indicate 
that the workers are more timid than those of the P. 
ferrugineus group. One might surmise that its hab- 
its are similar to those of P. nigropilosus, although 
the two species do not appear to be one another's 
closest relatives (Ward 1991). 

Pseudomyrmex subtilissimus (Emery 1890) 

Pseudomyrmex simulans Kempf 1958 
(Fig. 9) 

Pseudomyrma subtilissima Emery 1890:65. Lecto- 
type worker, Alajuela, Costa Rica (Alfaro) 



(MCSN) [Examined]. 

Pseudomyrmex subtilissimus (Emery 1890);Kempf 

Worker diagnosis. A member of the P. 
subtilissimus group, and immediately distinguish- 
able from all other acacia-associated Pseudomyrmex 
by its small size (HW < 0.60), elongate head (CI < 
0.66), apedunculate petiole, and scarcity of stand- 
ing pilosity. See Ward (1989:432) for further dis- 
cussion of this species. 

Distribution and biology. P. subtilissimus has 
been collected only in Nicaragua and Costa Rica. 
What little is known about its biology suggests that 
it is a timid, non-protective species living in the 
thorns of Acacia plants occupied by (declining?) 
colonies of P. flavicornis. 


The 47-character data set used for cladistic analy- 
sis of the P. ferrugineus group is given in Table 2. 
Implicit enumeration by Hennig86, using the ie* 
command, yielded a single most parsimonious tree 
of length 73, consistency index 0.86 (0.84 exclud- 
ing autapomorphies of ingroup species) (Fig. 73). 
This tree has an unresolved trifurcation involving 
five Pseudomyrmex species: ferrugineus, janzeni, 
and (flavicornis + (mixtecus + veneficus)). These 
five species together constitute what may be termed 
the P. ferrugineus complex. It is allied to the pair of 
sister species, P. spinicola and P. satanicus. The 
sister group of these seven species is the isolated 
and autapomorphous P. peperi. Finally, P. 
nigrocinctus and P. particeps make up a basal pair 
of species with relatively unspecialized morphol- 

Separate analyses of worker-, queen-, and male- 
based data sets produced trees in substantial agree- 
ment with these findings and largely congruent 
with one another (Figs. 74-76). This indicates that 
some confidence can be attached to the main fea- 
tures of the cladogram, and that homoplasy in 
worker and queen morphology possibly due to 
parallel selection pressures during diffuse coevolu- 
tion of the ant/acacia interaction (see below) has 
not been so rampant as to obscure all evidence of 

relationship, since both castes point to a cladistic 
pattern similar to that derived from male morphol- 
ogy (primarily male genital characters). Disagree- 
ment revolves around the position of taxa within the 
P. ferrugineus complex. Worker morphology sug- 
gests that P. mixtecus is more closely related to P. 
flavicornis than to P. veneficus. The male character 
set supports a (P. mixtecus + P. veneficus) pairing 
and is uninformative about other relationships within 
the P. ferrugineus complex. The queen-based tree is 
identical in topology to that based on all characters, 
i.e. it supports (P. flavicornis + (P. mixtecus + P. 
veneficus)) but does not resolve relationships among 
P. ferrugineus, P. janzeni, and the foregoing trio. 
The inferred phylogeny of the P. ferrugineus 
group (Fig. 73) suggests that speciation has oc- 
curred primarily as a consequence of geographical 
isolation. Of the three pairs of sister species, two (P. 
nigrocinctus + P. particeps, P. mixtecus + P. 
veneficus) are composed of allopatric species (Figs. 
69, 72), while the ranges of the third pair (P. 
spinicola and P. satanicus) are more or less con- 
tiguous (Fig. 68). The trio of species comprising (P. 
flavicornis + (P. mixtecus + P. veneficus)) also have 
entirely non-overlapping distributions, and they 
point to the importance of geographical barriers in 
southwestern Mexico to speciation in this complex 
(Fig. 69). This is also indicated by the distributions 
of P. ferrugineus and P. janzeni, the latter an 
allopatric isolate in western Mexico (Fig. 70), al- 
though it should be noted that the cladistic analysis 
did not confirm a sister group relationship between 
these two phenetically similar species. At higher 
levels in the cladogram there is some geographical 
overlap between taxa, but dispersal has not been so 
extensive as to obliterate all evidence of vicariance. 
Within the P. ferrugineus complex, for example, P. 
flavicornis and relatives are largely confined to the 
Pacific slopes of Mesoamerica in contrast to the 
more eastern distribution of P. ferrugineus (Figs. 
69-70). The P. ferrugineus complex itself is centred 
in northern Central America, with only one species 
(P. flavicornis) occurring south of Honduras, as far 
as Costa Rica in this case, while its sister group (P. 
spinicola and P. satanicus) occurs primarily south 
of Honduras and extends all the way to northern 
Colombia (Fig. 68). This suggests an historical 
barrier somewhere in the region of present day 

VOLUME 2, NUMBER 1, 1993 


Honduras or Nicaragua which split these two clades. 
The most basal divisions within the P. ferrugineus 
group involve much more extensive geographical 
overlap, making any historical inferences difficult. 
The distributions of the species P. peperi and P. 
nigrocinctus are consistent with an origin and early 
diversification of the P. ferrugineus group in either 
northern or central Mesoamerica. The timeframe 
for this is unknown but presumably occurred prior 
to the formation of the Panamanian land bridge (i.e. 
before early Pliocene or late Miocene). Early diver- 
sification in the group may have been encouraged 
by the presence of an island archipelago in the 
region (Donnelly 1992). 

Finally, we come to the question of whether the 
phylogenies of the acacia-ants and their host aca- 
cias are congruent. A phylogeny of the swollen- 
thorn acacias is not available but Janzen's (1974) 
revision contains some relevant information. Janzen 
(1974) concluded that the Central American swol- 
len-thorn acacias are polyphyletic, i.e. that 
myrmecophy tism arose more than once or that non- 
myrmecophytic acacia species independently ac- 
quired myrmecophytic traits through hybridiza- 
tion. He also noted (Janzen 1966) that individual 
species of acacia can be associated with more than 
one Pseudomyrmex species and vice versa. None of 

this leads one to expect a pattern of co-speciation, 
and mapping known host associations on the 
Pseudomyrmex cladogram (Fig. 73) confirms the 
opportunistic nature of the interaction. It seems that 
most species in the Pseudomyrmex ferrugineus 
group occupy any swollen-thorn acacia species 
available to them. On the other hand, the possibility 
of locally non-random associations between ants 
and available plants, perhaps mediated by compe- 
tition, deserves investigation. 

Three species of acacia-ants, P. janzeni, P. 
particeps and P. satanicus, are confined to a single 
acacia species (A. hindsii, A. allenii and A. 
melanoceras, respectively), the former (P. janzeni) 
almost certainly because of its limited geographical 
distribution but the last two because of their appar- 
ent specialization on the acacia or the forest habitat 
to which it is restricted. Populations of other swol- 
len-thorn acacia species occur within the probable 
dispersal ranges of alate queens of P. particeps and 
P. satanicus but are apparently not colonized. These 
two host-specific Pseudomyrmex have the smallest 
ranges of any members of the P. ferrugineus group 
and are clearly the most endangered. 


Table 2. Data set used for cladistic analysis of the_Pseudomyrmex ferrugineus group. P. fervidus served 
as outgroup (see text)."?" signifies polymorphism or ambiguity in expression of the character state. 
Characters 12, 13 and 16 were considered unordered. 












































































4 13 1431 36 

nil I 

all characters 
(length 73 ci 0.86) 

7 8 9 12 34 40 42 43 44 45 46 
I I I I I I I I I I I 

3 4 9 11 12 13 16 24 26 30 38 47 

i B i i i i i n i i i 

3 6 22 

11 21 22252529324246 
I I I I I I I I I 

1 25 152833 
I I I I I I 

17 37 38 43 
I I I I 


24252639 || 16 18 

=H I I " I 


particeps al 









cr ge gl hi 


al cl cr 

ch cl co cr ge gl hi ma sp 


cl cr hi 
cl hi 

cl hi 


worker characters 
(length 29 ci 0.89) 


queen characters 
(length 33 ci 0.75) 


male characters 
(length 28 ci 0.96) 

Figs 73-76. Phylogenetic relationships of the obligate acacia-ants, Pseudomyrmex ferrugineus group. 73: 
cladogram based on the entire 47-character data set (Table 2), with character state changes indicated and with host 
plant associations listed for each species. Solid bars: unique forward changes; hatched bars: homoplasious forward 
changes; open bars: reversals. There are alternative, equally parsimonious reconstructions of character state change 
for characters 4, 12, 16, 38 and 46. By reference to other Pseudomyrmex species, most changes occurring between 
the outgroup (P.fervidus) and the ingroup (i.e. changes in characters 10, 19, 23. ..47) are probably synapomorphies 
of the latter, but one character state (27.0) appears to be aderived feature of P.fervidus. The following abbreviations 
are used for host plants: al = Acacia allenii, ch = A. chiapensis, cl = Acacia collinsii, co = A. cooki and A. janzenii, 
cr = A. cornigera, ge = A. gentlei, gl = A. globulifera, hi = A.hindsii, ma = A. mayana, me = A. melanoceras, sp = 
A. sphaerocephala. 74-76: cladograms based on the worker, queen and male character sets, respectively. 

VOLUME 2, NUMBER 1 , 1 993 


This systematic study of Pseudomyrmex ants 
associated with swollen-thorn acacias in Central 
America demonstrates that the primary group of 
obligate acacia-ants (the P. ferrugineus group) is 
monophyletic and comprises 1 species. Four addi- 
tional unrelated Pseudomyrmex species, from two 
other species groups, have become secondary spe- 
cialists on the acacias. These latter species appear to 
be parasites or commensals but little is known 
about their biology (except P. nigropilosus). These 
14 specialists are joined by at least six generalist 
twig-nesting Pseudomyrmex which occasionally 
colonize acacia thorns. 

The well known mutualism between ants and 
Central American acacias applies with certainty 
only to members of the P. ferrugineus group and 
their associated plants. Within this group experi- 
mental evidence of a mutualism is available only 
for the P. ferrugineus x A. cornigera interaction 
(Janzen 1966, 1967b), although the biology and 
behavior of the other nine species of ants suggest 
that they also provide important protection to their 
host acacias under most conditions. Cladistic analy- 
sis of the P. ferrugineus group, coupled with a 
consideration of host plant associations, indicates a 
pattern of diffuse coevolution, not one-on-one 
cospeciation (see also Janzen 1 966). It seems likely 
that the original obligate acacia-ant (the common 
ancestor of the P. ferrugineus group) underwent 
coevolution with its acacia host, but since then 
speciation and diversification of the two groups 
have been decoupled the swollen-thorn acacias 
are apparently even polyphyletic (Janzen 1974) 
and there has been much opportunistic pairing of 
ants and plants. Such liberal sharing of partners has 
presumably made the association susceptible to 
invasion by other Pseudomyrmex and Acacia lin- 

At the same time the key features of the system 
absolute dependence of ants in the P. ferrugineus 
group on acacia plants, the reliance of at least some 
(probably most) of the swollen-thorn acacia spe- 
cies on ants for normal growth and reproduction, 
and the suite of mutually beneficial traits exhibited 
by both partners mark this as one of the more 
impressive insect/plant mutualisms known. 


I thank the following persons for access to collec- 
tions under their care: J. Newlin (ANSP), B. Bolton 
(BMNH), M. A. Tenorio (CASC), H. A. Hespenheide 
(CHAH), R. Ayala (EBCC), F. Fernandez (FFIC), D. 
Quintero Arias (GBFM), A. Solis (INBC), J. T. Longino 
(JTLC), R. R. Snelling (LACM; also old loans to D. H. 
Janzen from AMNH, CISC, CUIC, GCWC, INHS, 
now returned to their original locations), R. Poggi 
(MCSN), S. Cover (MCZC), C. Besuchet(MHNG), J. C. 
Weulersse (MNHN), C. R. F. Brandao (MZSP), M. 
Brancucci (NHMB), M. Fisher (NHMV), D. R. Smith 
(USNM), W. P.MacKay (WPMC), F. Koch (ZMHB), O. 
Lumholdt (ZMUC), D. R. Abraham (ZMUH) and E. 
Diller (ZSMC). Special tribute should be paid to Dan 
Janzen whose prodigious efforts in the field yielded a 
collection of acacia-ants unprecedented in size and scope, 
together with much valuable biological information. I 
am particularly grateful to Jack Longino and Roy Snelling 
who facilitated my study of the Janzen collection in 
LACM. I also received useful acacia-ant material from 
Gary Alpert, Diane Davidson, Alain Dejean, Linda 
Farley, Doug Gill, Frank Joyce, Alex Mintzer, Dave 
Olson, Steve Schoenig, Walter Tschinkel and Dave 
Whitacre. This research was supported by NSF grant 


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Errata for: Ward, P. S. 1993. Systematic studies on Pseudomyrmex acacia-ants. J. Hym. Res. 

Due to a printer's error all " ^ ", " <, " and " ~ " signs in this paper were replaced by blanks 
(although these symbols were present in the page proof), resulting in a significant loss of 
information. The affected text follows. 

p. 121, column 2, line 30 "PLI2 ^ 0.77" 

p. 121, column 2, line 45 "worker PLI ^ 0.71, queen PLI St 0.64" 

p. 122, column 1, line 36 "HW < 0.85" 

p. 122, column 1, line 37 "HW ^ 0.85" 

p. 122, column 1, line 41 "PL/HW k 0.71" 

p. 122, column 2, lines 8-9 "CI St 0.94 and/or HW 5: 0.96" 

p. 122, column 2, line 15 "SL/HL 5: 0.22" 

p. 122, column 2, line 16 "SL/HL 0.21" 

p. 130, line 33 "CI 1.12" 

p. 130, line 35 "CI 0.80" 

p. 132, line 40 "SL/HL ^ 0.21" 

p. 132, line 42 "SL/HL ^ 0.22" 

p. 133, lines 4-5 "CI 5: 0.94 and/or HW Ss 0.96" 

p. 133, column 1, line 8 "MD8/MD9 0.70" 

p. 133, column 1, line 11 "MD4/MD5 0.74" 

p. 135, column 2, line 4 "worker REL ^ 0.50, queen REL ^ 0.48" 

p. 135, column 2, lines 5-6 "worker PLI 0.71, queen PLI ^ 0.63" 

p. 135, column 2, lines 29-30 "queen PLI 0.65, queen PL/HL 0.49" 

p. 145, column 1, lines 26-27 "REL 0.45, REL2 < 0.56, EL/LHT ^ 0.61" 

p. 145, column 1, line 30 "FCI 0.055" 

p. 145, column 2, lines 7-8 "worker PWI3 ^ 0.50, worker PPWI s 1.30" 

p. 146, column 2, line 10 "CI 0.61" 

p. 146, column 2, line 12 "LHT/HW 1.12" 

p. 152, column 2, lines 14-15 "(^ 0.10 mm)" 

p. 155, column 1, line 20 "REL 0.66" 

p. 157, column 1, lines 20-21 "PLI 0.55" 

p. 157, column 2, line 12 "MD8/MD9 0.70" 

p. 157, column 2, line 17 "MD4/MD5 0.65" 

p. 158, column 1, lines 7-8 "PWI3 0.60" 

p. 158, column 1, line 41 "REL 0.65" 

p. 158, column 1, lines 42-43 "MFC 0.02" 

p. 158, column 1, line 44 "CI 0.85" 

p. 159, column 1, line 3 "CI 1.12" 

Another printing error resulted in the loss of data in column 31 of Table 2 (p. 163): 
Pseudomyrmex nigroclnctus and P. particeps should be coded "1", not "0", for character 31. 

Other corrections: 

p. 121, column 1, line 41 
p. 131, line 34 

For "public domain software" read "Shareware software" 
For "Figs. 10, 34" read "Figs. 11, 34"