ote

JHR 50: 8 1-95 (20 I 6) JOURNAL CF Apeenreviewed open-access journal
Sie ices (4) Hymenoptera

http://jhr.pensoft.net The insertional Society of ymenopterists RESEARCH

Morphology of the male genitalia of Brachymyrmex and
their implications in the Formicinae phylogeny

Christopher M. Wilson', Autumn Smith-Herron’, Jerry L. Cook'

| Sam Houston State University, Department of Biological Sciences, 1900 Ave. I Huntsville TX, USA 2. Texas
Invasive Species Institute, Sam Houston State University, PO Box 2506, Huntsville TX, USA

Corresponding author: Christopher M. Wilson (christopher.wilson2@unt.edu)

Academic editor: Michael Ohl | Received 7 April 2016 | Accepted 25 May 2016 | Published 27 June 2016
http://zoobank. ore/D4734A85-8600-4046-94F5-4364FD7D8E36

Citation: Wilson CM, Smith-Herron A, Cook JL (2016) Morphology of the male genitalia of Brachymyrmex and their
implications in the Formicinae phylogeny. Journal of Hymenoptera Research 50: 81-95. doi: 10.3897/JHR.50.8697

Abstract

The male genitalia of Brachymyrmex are examined and terminology clarified. We document two confor-
mation groups based on the lateral carina, conformation 1 has a complete lateral carina that reaches the
apex of the valviceps and in conformation 2 the lateral carina is broken with the apical end projected
dorsally. Previously documented species are evaluated in the context of this new information. We offer
support for the movement of Brachymyrmex into the resurrected tribe Myrmelachistini based on the mor-
phology of the penisvalvae, and offer definitive methods of assigning unknown specimens to this genus.
This study provides histological methodologies for the preparation, differentiation, and permanent storage

of minute ant genitalia structures and the associated musculature.

Keywords
Brachymyrmex, genitalia, morphology, penisvalvae, phylogeny

Copyright Christopher M. Wilson et al. This is an open access article distributed under the terms of the Creative Commons Attribution License
(CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

82 Christopher M. Wilson et al. / Journal of Hymenoptera Research 50: 81—95 (2016)

Introduction

The ant genus Brachymyrmex Mayr, 1868 exists in a state of taxonomic confusion.
The small workers are notably devoid of good species delineating characters, and their
distributions are not well represented in collections. This “miserable little genus”
(Creighton 1950) has been largely ignored in systematic myrmecological works. Cur-
rently there are 60 valid species, of which only 21 contain male descriptions, and five
of these have genitalia illustrations. The male genitalia offer species level characters that
are desperately needed for this taxonomically challenging group (Quiran et al. 2004).
In order to utilize the characters to the best of our ability we must first understand
their morphology. Boudinot (2013) has provided a comprehensive review of the mor-
phological structures and musculature associated with ant male genitalia, allowing for
comparative studies across ants as a group.

Taxonomic history of Brachymyrmex

Brachymyrmex was described by Mayr (1868) from the type species Brachymyrmex pa-
tagonicus. Forel (1878) included Brachymyrmex in the subfamily Camponotinae, and in
the tribe Plagiolepidini (Forel 1893). Ashmead (1905) included the Plagiolepidini in the
subfamily Formicinae. Forel (1912) erected the tribe Myrmelachistini and defined the
tribe as having females with an atennomere count of 9 or 10, males being 10 or 1 1-mer-
ous, and included the genera Aphomyrmex, Brachymyrmex, Myrmelachista, and Rhopalo-
myrmex. Emery (1925) redefined the Myrmleachistini as having fewer than 12 anten-
nomere, with a distinct antennal club. This redefinition removed Brachymyrmex from the
Myrmelachistini and Emery placed it in the tribe Dimorphomyrmicini. Emery included
along with Brachymyrmex, the genera Aphomomyrmex, Cladomyrma, Dimorphomyrmex,
and Gesomyrmex, based on the 8 to 9 merous antennomere count lacking an antennal
club, short frontal carinae, and large eyes. Emery further considered Aphomyrmex, Bra-
chymyremx, and Cladomyrma to be closely related and had them comprise the subtribe
Brachymyrmicini. Wheeler (1929) treated Dimorphomyrmex as a junior synonym of Ge-
somyrmex, and concluded that Gesomyrmex was not closely related to the other members
of Dimorphomyrmicini. As a result Wheeler raised Emery’s subtribe Brachymyrmicini
to tribal status, and resurrected Gesomyrmicini to include Gesomyrmex. Wheeler and
Wheeler (1976, 1985) concluded Aphomomyrmex, Brachymyrex, Cladomyrma, Eupre-
nolpis, Paratrechina, Petelomyrmex, Prenolepis, and Stigmacros to be in the Brachymyrmi-
cini, using larval characters. Agosti (1991) placed Brachymyremx within the Pseudolasius
genus-group defined by widely separated hind coxae, the petiole ventrally u-shaped, a
simple helcium which is antero-ventraly often concealed by the anteriorly fused sternite
and tergite. Bolton (2003) transferred Brachymyrmex to the Plagiolepidin. Recently Ward
et al. (2016) transferred both Brachymyrmex and Myrmelachista to the Myrmelachistini,
which they resurrected. Ward et al. define this group as having the following shared
worker characters: a reduced antennomere count (9—10-merous), five mandibular teeth,
petiolar node inclined anteriorly, with the base of abdominal segment HI completely

Morphology of the male genitalia of Brachymyrmex and their implications... 83

fused tergosternally on each side of the helcium, and a plesiomorphic 6,4 palp formula
that is reduced to 5,4 in some Myrmelachista (Ward et al. 2016).

Santschi (1923) provided the last revision of the group, designating many new
species and subspecies. His descriptions, however, are of little value, as they are short
and include few comparative characters. In his revision Santschi erected the subgenus
Bryscha, which he defined by having dimorphic workers, short and flared sepals of the
proventriculus, and erect hairs on the scape and legs. Bryscha was provisionally syn-
onymized under Brachymyrmex by Brown (1973). Although most Brachymyrmex have
monomorphic workers; at least two species are dimorphic and Bryscha may need to be
resurrected (Ortiz and Fernandez 2014).

The genus has a wide diversity of life histories. Most species are generalist nesters
that nest in leaf litter, under stones, or under bark; at least two species have a distinct
replete caste; while others are arboreal nesting under epiphyte mats or in small plant
cavities. By contrast, the closely-related Myrmelachista are obligate arboreal nesting
ants (Longino 2006).

As our understanding of ant evolution progresses, the need for additional taxo-
nomic and systematic information is increasing. The primary source for morphological
characters in ants is worker morphology. ‘This trend is easy to understand as workers are
ubiquitous in the environment, often being the only caste collected and certainly the
most prevalent. Queens and males on the other hand are less-frequently encountered,
as they are usually within nests or produced only for brief periods. The reproductive
casts have thus been largely neglected. Males are largely ignored, and therefore repre-
sent an untapped source of morphological characters for taxonomic and phylogenetic
use. Moreover, when collected, males may be difficult or even impossible to associate
with their workers. However, males may be associated through careful collecting and
molecular phylogenies. A recent movement among ant researchers has been to pay
more attention to males, both when collecting in the field and unassociated males
(Boudinot 2013, Boudinot 2015, Deyrup and Cover 2004, LaPolla et al. 2012, and
Yoshimura and Fisher 2007, 2009, 2012).

The most useful character for males are arguably the genitalia, and males, like
workers, range in size from the Dorylus “sausage flies” to remarkably small Brachy-
myrmex. Viewing and manipulating the male genitalia of larger species is often simple
enough; most genitalia are even large enough to point mount for permanent storage.
Smaller species, however, are neither simple to manipulate nor store. This has led some
authors to not fully dissect the genitalia from small males obtaining images in situ ei-
ther through compound microcopy or scanning electron microscopy (SEM) (LaPolla
et al. 2012, and Ortiz and Fernandez 2014). With the high cost and low availability
of SEM, stereoscopic microscopy is more available, although resolution at 40x is often
poor. Due to the low resolution at this magnification, small genitalic structures tend
to blend together and become difficult to interpret in situ. While there is value in the
structure of an intact genital capsule, there remains a large portion of both the volsella,
and penisvalva that cannot be viewed, losing potentially important characters.

Here we present methods for dissection and permanent storage via slide mounting
of small ant genitalia, with an additional option for muscle fixture and the ability to

84 Christopher M. Wilson et al. / Journal of Hymenoptera Research 50: 81-95 (2016)

clear structures for SEM. Slide mounting genitalia allows examination at much higher
magnifications than under stereoscopic microscopy, without the need for sputter coat-
ing or environmental SEM prep. Additionally the remainder of the specimen remains
intact, losing, at most, only the last three segments. Notes on the genitalia of Brachy-
myrmex and their implications on the Formicinae phylogeny are presented using the
described dissection methodologies. It is our hope that this paper provides a greater
understanding of the male genitalia characters for Brachymyrmex, and encourages re-
newed interest in this “miserable little genus”.

Materials and methods

Tissue sampling

For this study we sampled 16 species/morphospecies of Brachymyrmex, specimens were
taken from the first author’s personal collection (CMWC), the Sam Houston State
University Entomology Collection (SHSUE), the John T. Longino collection (JTLC),
or accessed via AntWeb.org. Specimens from the collections were either in 95% EtOH
or dried. Once dissected, bodies without genitalia were returned to the collections
dried and point mounted, with the genitalia deposited in the CMWC on slides. The
genitalia where dissected under an Olympus SZX12 dissecting microscope with a max-
imum 115x magnification mounted with a Olympus DP72 camera. Examined under
an Olympus BX53 compound microscope with 10x, 40x, and 60x planapochromat-
ic objectives with differential interference contrast prism mounted with a Olympus
DP72 camera, and an Olympus B-Max 41 compound microscope with 10x, 40x, and
60x, with universal and planapochromatic objectives with either bright-field or phase-
contrast condenser mounted with a Olympus DP-12 camera. Additional specimens
were prepared for SEM using a Vega Scan high vacuum micrograph. Photos taken
with the aforementioned cameras were stacked by hand using Adobe Photoshop CS6.

Microtechnique

The procedures for the unstained whole mounts are as follows. The terminal segments
of male reproductive organs were removed with a surgical scalpel and size 000 insect
pins. Tissues were transferred and presoaked in a 20% sodium hydroxide (NaOH)
solution for ca. 30 minutes to dissolve muscle and soft tissues. The remaining sclerites
were neutralized with a 20% solution of Acetic acid (C,H,O,) for 5 minutes. Dehydra-
tion of tissues was initiated in 70% ethanol and continued at 20 min intervals through
a graded series of ethanol washes, ending in two final washes with 100% ethanol. Tis-
sues were cleared to near transparency with an initial introduction to xylene via a 50:50
solution of xylene:ethanol, and two 20 minutes washes in histological grade xylene.
Prepared specimens were permanently mounted with dammar balsam mounting me-

Morphology of the male genitalia of Brachymyrmex and their implications... 85

dia. Alternatively, specimens can be directly taken form 100% ethanol and mounted in
euparal. Slides are placed on a pre-warmed slide warmer and allowed to cure overnight.

The procedures for stained whole mounts are as follows. The terminal segments
of male reproductive organs were removed with a surgical scalpel and size 000 insect
pins. In order to examine the insertion and attachment sites for all muscles, excised
tissues were not dissolved. Hydration of reproductive tissues were initiated in 70%
ethanol and regressed to a final wash in deionized water. Prepared tissues were stained
for 20 minutes in Harris Hematoxylin (without counterstain), and washed in an acid
alcohol de-stain for 5—10 seconds. Stained tissues were then dehydrated with ethanol
through an ascending graded series, cleared in xylene and permanently mounted with
Damar Balsam mounting media. Examination of prepared tissue mounts follows the
description above. The figures presented here are grouped by similar morphology and
grouping statements accompany the respective figures.

Results

The terminology herein follows Boudinot (2013). The genital capsule is composed of
three paired valves, sternum IX, and the cupula. Working from medial to lateral we find
a paired median valve termed the penisvalva, each segment of the penisvalva is com-
posed of an arm-like apophysis termed the valvura, and the distal components or valvi-
ceps. The paired penisvalvae are joined dorsomedially by the penisvalva membrane. On
either side of the penisvalva are the paired volsellae, which are attached to the basimere
via the basivolsella and volsellar membrane. The volsellae themselves are composed of
the parossiculus, the cuspis, and the digitus which is basolaterally articulated with the
parossiculus. The lateral most paired valves are the parameres, which are composed of
a large dish like basimere, and an elongated distal telomere. ‘The cupula is a small thin
sclerite attached to abdominal tergum IX and the vollsella, and is easily left behind
when removing the genital capsule. We have not examined the cupula of Brachymyrmex.

Penisvalvae

The paired penisvalvae of Brachymyrmex show tremendous variation in general shape,
ranging from scimitar, to sickle-shaped, and quadrate. All species in which the males
have been examined show dentition on the ventral ridge of the penisvalvae, which is
conspicuously absent in Myrmelachista (though it should be noted that dentition is
present throughout many of the formicids) (Fig. 1).

LaPolla and Longino (2006) suggest that the dorsal placement of the apodemal
ridge in Brachymyrmex, Cladomyrma, and Myrmelachista as a potential synapomorphy
for these three genera. A clarification of terms is needed. The penisvalva is composed
of two parts, the valvura and the valviceps. The valvura bears all of the muscular in-
sertions, and is an internal aphophysis while the valviceps is an external blade like

86 Christopher M. Wilson et al. / Journal of Hymenoptera Research 50: 81-95 (2016)

A B C

100 um 50 um 50 um

ea 30 um 100 um

100 um 50 um

50 um

Figure |. Ectal views of the right penisvalvae of Myrmelachista sp. A Brachymyrmex CMW-012 B Brachy-
myrmex patagonicus C Acropyga exsanguis D Stigmacros sp. E Camponotus tonduzi F Lasius sp. G Gigantiops
destructor H Prenolepis impairs \ Black Arrows lateral apodeme, Red Lines lateral carinae.

structure. The insertion of muscle & (= dorsal gonostyle/volsella complex penisvalval
muscle) delimits the valvura posterodorsally.

As the base of the valvura is produced laterally, it may be referred to as the “lateral
apodeme” (Fig. 1). Muscles 7 (= ventroapical parameral-penisvalvar muscle) and / (=
lateral parameral-penisvalvar muscle) attach to the penisvalva via the lateral apodeme.
The apodeme and its associated musculature allow the penisvalvae to pivot on the me-
diosagittal plane. The lateral apodeme in most ants is situated at the anterior end of a
lateral carina (referred to by Lapolla and Longino as the “apodemal ridge”). ‘This lateral
carina is on the external surface of the valviceps (i.e. is not internal) and therefore can-
not be an apodeme. ‘The lateral carina cups the volsella dorsally iv situ, and is a structure
which displays taxonomically valuable variation. Additionally the “dorsally placed” ca-
rina (““apodemal ridge”) interpretation of Lapolla and Longino (2006) is anatomicaly
imprecise and suggest that the lateral caraina has migrated dorsally to a position which
is dissimilar to other Formicinae. Instead, it is apparent that the lateral carina is un-
modified in position and that, rather, the anterodorsal region of the valviceps has been
reduced such that the lateral apodeme delimits the valviceps anterodorsally.

Morphology of the male genitalia of Brachymyrmex and their implications... 87

Figure 2. External genitalia of Brachymyrmex patagonicus, compound light microphotograph of the pe-

nisvalva in ectal view A lateral view of the genital capsule with the telomere pulled back to reveal the
volsella and penisvalva B SEM of the penisvalva in ectal view C magnified ectal view of the penisvalva
showing the separation of the valvura, the proximal end of the lateral carina, and severed muscular tissue
form muscles &, and i D dorsal view of the genital capsule E apical view of the genital capsule F Colors:

Blue penisvalvae; Green volsella; Red telomere; Purple baismere.

Two main conformation patterns can be seen in the penisvalval morphology
among the Brachymyrmex we sampled. In conformation 1 the lateral carina is com-
plete, running from the lateral apodeme to the apex of the valviceps. In this conforma-

88 Christopher M. Wilson et al. / Journal of Hymenoptera Research 50: 81-95 (2016)

20 um. 50 pm 50 um
— — —

50 pm 100 pm 100 jum.
————

Figure 3. Paramere, volsella, and penisvalva of Brachymyrmex obscurior A-—C Brachymyrmex cored-
moyi (basimere not present) AntWeb.org, CASENT0740911 Photograped by Veronica M. Sinotte
D-F Grouping: lateral carinae complete; digitus elongate and bifurcate apicaly; valvura parallel to the

long axis of the valviceps.

tion group the lateral carina forms a sharp curve dorsally near the carina’s base (Fig.
1C). This group includes Brachymyrmex cordemoyi Forel, 1895, B. patagonicus and
Brachymyrmex obscurior Forel, 1893 (Figs 2A, 3C, F). The general shape, most notably
the lack of a raised anterior portion along the valvicpes blade, can also be seen in the
illustrations of Brachymyrmex brevicronis Emery, 1906 (Quiran 2005), Brachymyrmex
bruchi Forel, 1912, and Brachymyremx oculatus Santschi, 1919 (Quiran et al. 2004).
This conformation is rather distinct among the Formicinae which tend to have a fairly
flat, or gently forming a convex lateral carinae (Fig. 1D-—I).

The lateral carina of conformation 2 is incomplete being broken apically of the lat-
eral apodeme into an anterior portion, which is continuous with the lateral apodeme,
and a posterior portion that is raised dorsally above the blade of the valviceps (Fig. 1B).
This conformation group includes all other taxa we examined (Figs 4-6). The broken
lateral carina is almost certainly unique and is likely to be a synapomorphy for spe-
cies with this morphology. Though this is a tentative evaluation that requires further
sampling to fully elucidate.

Quiran's (2007) illustration of Brachymyrmex australis Forel, 1901 is difficult to place
in either conformation group. The penisvalvae illustration lacks a raised anterior portion,
however the lateral carina is not indicated, furthermore the volsella is similar to those in
conformation 2, with a medial concavity (see discussion of the volsella below). Ortiz and
Fernandez's (2014) description, and accompanying figure for the male of Brachymyrmex
pilipes Mayr, 1887 is inconclusive. The majority of the valviceps is covered by the tel-
omere, and the volsella is completely hidden. That being said, the dorsum of the apical
end of the valviceps does appear to be projected upwards, as we see in conformation 2.

Morphology of the male genitalia of Brachymyrmex and their implications... 89

pe 20 um Jo um
D E F
aS
; gt >
Ve (a ele
G H I

50 um 20 um jun
—

Figure 4. Paramere, volsella, and penisvalva of Brachymyrmex CMW-011 (basivolsella fragmented)
A-C Brachymyrmex CMW-012 (basivolsella fragmented) D-F Brachymyrmex cavernicola G-1 Brachy-
myrmex heeri J-L Grouping: lateral carinae broken; digitus elongate, apex curving ventrad and not bifur-
cate apically; valvura oblique to the long axis of the valviceps.

Volsella

The volsella of Brachymyrmex follows the pattern of some Myrmelachista where the
cuspis is reduced to a small triangular protrusion affixed to the wall of the digitus
(B. obscurior, (Fig. 3B) B. CMW-006, B. CMW-003, B. CMW-008, B. CMW-010,
(Fig. 5B, E, H, K) B. JTL-004, B. JTL-005, and Brachymyrmex depilis Emery, 1893
(Fig. 6H, K)), or completely absent (B. CMW-007, B. CMW-009 (Fig. 6B, E)). Un-
like Myrmelachista, there is little variation in the cuspis, though in some species the
cuspis is slightly protruded (B. CMW-011, B. CMW-012, Brachymyrmex cavernicola
Wheeler, 1938 and Brachymyrmex heeri Forel, 1874 (Fig. 4B, E, H, K)). Brachymyrmex

90 Christopher M. Wilson et al. / Journal of Hymenoptera Research 50: 81-95 (2016)

A B C
~
ING ZN
— Le AN e
a Ea Sey
S = Ley
20pm 20 um 20 um.
D E F
& :
\() Ss
aS = \
: ae ss)
ee
20 um 20 um 20 wm
G H I
SES aN
20 um 20 um 20 um
J K L
P Ts y
he 2 cy
i. eee : \
Nar Ong S ES «
——— elt. eS Ny
i oe
20m, 20 um. 20 wm

Figure 5. Paramere, volsella, and penisvalva of Brachymyrmex CMW-006 (basivolsella fragmented) A-C Bra-
chymyrmex CMW-003 D=F Brachymyrmex CMW-008 G-=k: Brachymyrmex CMW-010 J—L Grouping: lateral

carinae broken; digitus lobate; valvura perpendicular to the long axis of the valviceps.

cordemoyi is unique amongst the specimens we examined, the cuspis is ovate, and well
developed (in regards to Brachymyrmex), and a number of flexuous setae are present
(Fig. 3E). In addition the digitus also bears setae, which is similarly unique. A row of
flexuous setae is present ventromedially on the basivolsella in all taxa we examined and
can serve as a method of orienting the dissected volsella. The shape of the digitus ranges
from a subtriangular, or subquadrate short broad projection (B. patagonicus (Fig. 7C),
B. CMW-006, B. CMW-003, B. CMW-008, B. CMW-010 (Fig. 5B, E, H, K)) toa
long narrow structure with the apical portion either curving ventrad (B. CMW-0011,
B. CMW-0012, B. cavernicola, and B. heeri (Fig. 4B, E, H, K)), or bifurcate (B. cor-
demoyi, and B. obscurior (Fig. 3B, E)). The basivolsella is broadly flattened bending to

Morphology of the male genitalia of Brachymyrmex and their implications... 91

A
20 um 20 jm. 20 um.
D
>
or 4
20pm 20 um 20 um.
G H I
\
Ry) SSS
20 ym _ 20 um — 20 um
J K L
ps
i . Lf
‘ |) zy
|
y
20 um 20 pm
M

Figure 6. Paramere, volsella, and penisvalva of Brachymyrmex CMW-007 (basivolsella fragmented) A—C Bra-
chymyrmex CMW-009 (basivolsella fragmented) D-F Brachymyrmex JTL-004 (basivolsella fragmented)
G-I Brachymyrmex JTL-005 (basivolsella fragmented) J-L Brachymyrmex depilis (basivolsella fragmented)
M-O Grouping: lateral carinae broken; digitus lobate; valvura perpendicular to the long axis of the valviceps.

curve around the penisvalva (Fig. 2E, F), as a result of disarticulating the volsella from
the baimere the basivolsellae are prone to fragmentation this has been noted in the
figure legends were it has occurred.

92 Christopher M. Wilson et al. / Journal of Hymenoptera Research 50: 81-95 (2016)

B C

Figure 7. Ectal views of the volsella in Brachymyrmex depilis A Brachymyrmex CMW-011 B Brachymyr-
mex patagonicus C Red lines running from the dorsum of both the distal and apical ends of the volsella
not including the digitus.

The modification to the lateral carina of the valviceps seen in both conformation
groups seem to be related to the method in which the volsella rests against the valviceps
in situ. As a result the dorsal surface of the volsella in conformation 1 is unbroken,
while the dorsal surface of conformation 2 has a distinct concavity medially (Fig. 7)

Paramere

The telomeres are separated from the basimere by a membrane. Of the structures asso-
ciated with the genital capsule, the telomeres of Brachymyrmex show the least variation
in terms of overall shape and size. They are generally short and broad with numerous
elongate flexuous setae. Of the taxa we examined, the telomeres of B. CMW-007, and
B. CMW-009 (Fig. GA, D) are as broad as long and hemispherical in shape; those of
B. cavernicola, B. heeri, (Fig. 4G, J) B. CMW-006, B. CMW-003 B. CMW-008, B.
CMW-010 (Fig. 5A, D, G, J), B. CMW-012 (Fig. 4D), B. JTL-004, B. JTL-005, and
B. depilis (Fig. 6G, J, M) are slightly longer than broad and subtriangular; and those
of B. cordemoyi, B. obscurior (Fig. 3A, D) and B. CMW-11 (Fig. 4A) are longer than
broad, and finger like in shape. The basimere of Brachymyrmex are sub-triangular, and
broad dorsally. The basimere are also difficult to separate from the volsella completely
intact and often fragment.

Discussion

Our findings demonstrate that males of this genus may offer more taxonomic informa-
tion for understating the evolution within the genus, and for species delineations than
their worker counterparts. The morphology of the penisvalva lateral carina displayed
in the two conformation groups seen in Brachymyrmex likely represent two distinct
clades within the genus, and when compared on an intraspecific level there seems to
be little variation in genital morphology. Of course additional sampling is needed to
confirm this. In regard to the tribal position of Brachymyrmex in light of the conclu-

Morphology of the male genitalia of Brachymyrmex and their implications... 93

sive phylogeny of Blaimer et al. (2015) the characters that have previously been used
to unite various genera with Brachymyrmex, namely that of the reduced antennomere
count, and the reduction of the anterodorsal region of the valviceps must be considered
homoplasious.

Within Brachymyrmex Ortiz and Fernandez (2014) redescribed two dimorphic
species of Brachymyrmex, B. pilipes, and Brachymyrmex micromegas Emery, in Santschi,
1923. While these ants do fall within the current definition of the genus, the authors
raised questions as to the generic placement of these species. As noted previously their
figure for the male of B. pilipes is inconclusive, however it does outwardly resemble the
morphology seen in our conformation 2. Unfortunately the male of B. micromegas is
unknown. We hope that our work here stimulates future studies on these dimorphic
species to include dissected male genitalia, as these traits may help to accurately place
dimorphic species.

Future researchers collecting Brachymyrmex are encouraged to exhaustively, and
carefully hunt for males along with associated workers. Those running Malaise and
UV light traps should also be alert for male specimens. To that regard Brachymyrmex
holds a number of invasive ant species, B. patagonicus for example is a widespread
and has reached pest status in the United States (MacGown et al. 2007). The males
of this species can accumulate in UV light traps in the hundreds (Danny McDonald
personal communication). Our results here should be useful in obtaining a definitive
genus diagnosis, and in the United States our native species, B. depilis, belongs to con-
formation group 2 which is easily separated from the invasive B. patagonicus, and B.
obscurior both of which belong to conformation group 1. Outside of the United States
the uniqueness of Brachymyrmex genitalia should serve as a valuable tool for invasive
species detection with the implementation of general collecting methods.

Acknowledgments

The authors would like to thank Brendon Boudinot for reviewing earlier versions of
this manuscript, his comments substantially improved this work. We would also like
to thank Jack Longino for contributing much-needed specimens without which much
of this genus would still be a mystery.

References

Agosti D (1991) Revision of the oriental ant genus Cladomyrma, with an outline of the higher
classification of the Formicinae (Hymenoptera: Formicidae). Systematic Entomology 16:
293-310. doi: 10.1111/j.1365-3113.1991.tb00690.x

Ashmead WH (1905) A skeleton of a new arrangement of the families, subfamilies, tribes and
genera of the ants, or the superfamily Formicoidea. Canadian Entomologist 37: 381-384.
doi: 10.4039/Ent37381-11

94 Christopher M. Wilson et al. / Journal of Hymenoptera Research 50: 81-95 (2016)

Blaimer BB, Brady SG, Schultz TR, Lloyd MW, Fisher BL, Ward PS (2015) Phylogenomic
methods outperform traditional multi-locus approaches in resolving deep evolutionary his-
tory: a case study of formicine ants. BMC Evolutionary Biology 15: 257. doi: 10.1186/
s12862-015-0552-5

Bolton B (2003) Synopsis and classification of Formicidae. Memoirs of the American Entomo-
logical Institute 71: 1-370.

Boudinot BE (2013) The male genitalia of ants: musculature, homology, and functional mor-
phology (Hymenoptera, Aculeata, Formicidae). Journal of Hymenoptera Research 30:
29-49. doi: 10.3897/jhr.30.3535

Boudinot BE (2015) Contributions to the knowledge of Formicidae (Hymenoptera, Aculeata):
a new diagnosis of the family, the first global male-based key to subfamilies, and a treatment
of early branching lineages. European Journal of Taxonomy 120: 1-62. doi: 10.5852/
ejt.2015.120

Brown WL Jr. (1973) A comparison of the Hylean and Congo-West African rain forest ant
faunas. In: Meggers BJ, Ayensu ES, Duckworth WD (Eds) Tropical forest ecosystems in
Africa and South America: a comparative review. Smithsonian Institution Press, Washing-
ton, DC, 161-185.

Deyrup M, Cover S (2004) A new species of Odontomachus ant (Hymenoptera: Formicidae)
from inland ridges of Florida, with a key to Odontomachus of the United States. Florida En-
tomologist 87: 136-144. doi: 10.1653/0015-4040(2004)087[0136:ANSOOA]2.0.CO;2

Emery C (1925) Hymenoptera. Fam. Formicidae. Subfam. Formicinae. Genera Insectorum
183: 1-302.

Forel A (1878) Etudes myrmécologiques en 1878 (premiere partie) avec ’anatomie du gésier
des fourmis. Bulletin de la Société Vaudoise des Sciences Naturelles 15: 337-392.

Forel A (1893) Sur la classification de la famille des Formicides, avec remarques synonymiques.
Annales de la Société Entomologique de Belgique 37: 161-167.

Forel A (1912) Formicides néotropiques. Part VI. 5me sous-famille Camponotinae Forel. Mé-
moires de la Société Entomologique de Belgique 20: 59-92.

LaPolla JS, Kallal RJ, Brady SG (2012) A new ant genus from the Greater Antilles and Central
America, Zatania (Hymenoptera: Formicidae) exemplified the utility of male and molecular
systems. Systematic Entomology 37: 200-214. doi: 10.1111/j.1365-3113.2011.00605.x

LaPolla JS, Longino JT (2006) An unusual new Brachymyrmex Mayr (Hymenoptera: Formi-
cidae) from Costa Rica, with implications for the phylogeny of the Lasiine tribe group.
Proceedings of the Entomological Society of Washington 108: 297-305.

Longino JT (2006) A taxonomic revision of the genus Myrmelachista (Hymenoptera: Formici-
dae) in Costa Rica. Zootaxa 1141: 1-54.

MacGown JA, Hill JG, Deyrup MA (2007) Brachymyrmex patagonicus (Hymenoptera: Formi-
cidae), an emerging pest species in the southeastern United States. Florida Entomologist
90: 457-464. doi: 10.1653/0015-4040(2007)90[457:BPHFAE]2.0.CO;2

Ortiz CM, Fernandez F (2014) Brachymyrmex species with tumuliform metathroacic spiracles:
description of three new species and discussion of dimorphism in the genus (Hymenop-

tera: Formicidae). ZooKeys 371: 13-33. doi: 10.3897/zookeys.37 1.6568

Morphology of the male genitalia of Brachymyrmex and their implications... 95

Quiran EM, Martiez JJ, Bachmann AO (2004) The Neotropical genus Brachymyrmex Mayr,
1868 (Hymenoptera: Formicidae) in Argentina. Redescription of the type species, B. pata-
gonicus Mayr, 1868; B. bruchi Forel, 1912 and B. oculatus Santschi, 1919. Acta Zoolégica
Mexicana 20: 273-285.

Quiran EM (2005) El género Neotorpical Brachymyrmex Mayr (Hymenoptera: Formicidae) en
la Argentina. II: Redescripcién de las especies B. admotus Mayr, de B. brevicornis Emery y
B. gaucho Santschi. Systematics, Morphology, and Physiology 34: 761-768.

Quiran EM (2007) El género Neotorpical Brachymyrmex Mayr (Hymenoptera: Formicidae) en
la Argentina. II: Redescrpcién de las especies: B. aphidicola Forel, de B. australis Forel y B.
constictus Santschi. Systematics, Morphology, and Physiology 36: 699-706.

Ward PS, Blaimer BB, Fisher BL (2016) A revised phylogenetic classification of the ant sub-
family Formicinae (Hymenoptera: Formicidae), with resurrection of the genera Colobopsis
and Dinomyrmex. Zootaxa 4072(3): 343-357. doi: 10.11646/zootaxa.4072.3.4

Wheeler WM (1922) Ants of the American Museum Congo expedition. Bulletin of the Ameri-
can Museum of Natural History, New York, 1139 pp.

Wheeler WM (1929) The identity of the ant genera Gesomyrmex Mayr and Dimorphomyrmex
Ernest André. Psyche (Cambridge) 36: 1-12. doi: 10.1155/1929/71489

Wheeler GC, Wheeler J (1976) Ant larvae: review and synthesis. Memoirs of the Entomological
Society of Washington 7: 1-108.

Wheeler GC, Wheeler J (1985) A simplified conspectus of the Formicidae. Transactions of the
American Entomological Society 111: 255-264.

Yoshimura M, Fisher BL (2007) A revision of male ants of the Malagasy region (Hymenoptera:
Formicidae): Key to subfamilies and treatment of the genera of Ponerinae. Zootaxa 1654:
21-40.

Yoshimura M, Fisher BL (2009) A revision of male ants of the Malagasy region (Hymenoptera:
Formicidae): Key to genera of the subfamily Proceratiinae. Zootaxa 2216: 1-21.

Yoshimura M, Fisher BL (2012) A revision of the Malagasy endemic genus Adetomyrma (Hy-
menoptera: Formicidae: Amblyoponinae). Zootaxa 3341: 1-31.

Supplementary material |

Specimen locality data

Authors: Christopher M. Wilson, Autumn Smith-Herron, Jerry L. Cook

Data type: Specimen locality data

Explanation note: Locality data for dissected specimens.

Copyright notice: This dataset is made available under the Open Database License
(http://opendatacommons.org/licenses/odbl/1.0/). The Open Database License
(ODbL) is a license agreement intended to allow users to freely share, modify, and
use this Dataset while maintaining this same freedom for others, provided that the
original source and author(s) are credited.